DOC: Fix formatting of parameters
In the pandas API documentation, when the parameters are defined, they should be defined as:
```
Parameters
----------
name : str
    Description of the name parameter
```

Note that in `name : str` there is one space before the colon, and one after. This is important, because when the html documentation is rendered, if those spaces are not found, the name of the parameter is not splitted from the type, and everything is rendered as if everything was the name.

See for example in the `bins` parameter of `Series.hist` (note that in this case there are two of them, and the second should be removed, instead of fixing the spaces).

This happens in many docstrings, and it should be fixed to ensure that the documentation is rendered correctly.

We have a script to generate the whole list or cases where this happens:
```
./scripts/validate_docstrings.py --errors=PR10
pandas.read_msgpack: Parameter "encoding" requires a space before the colon separating the parameter name and type
pandas.read_excel: Parameter "engine" requires a space before the colon separating the parameter name and type
pandas.ExcelWriter: Parameter ".. versionadded" requires a space before the colon separating the parameter name and type
pandas.read_json: Parameter "chunksize" requires a space before the colon separating the parameter name and type
pandas.HDFStore.append: Parameter "format" requires a space before the colon separating the parameter name and type
pandas.read_feather: Parameter "use_threads" requires a space before the colon separating the parameter name and type
pandas.read_parquet: Parameter "columns" requires a space before the colon separating the parameter name and type
pandas.Series.asfreq: Parameter "fill_value" requires a space before the colon separating the parameter name and type
pandas.Series.plot.hist: Parameter "bins" requires a space before the colon separating the parameter name and type
pandas.Series.hist: Parameter "bins" requires a space before the colon separating the parameter name and type
pandas.Series.to_string: Parameter "header" requires a space before the colon separating the parameter name and type
pandas.DataFrame.asfreq: Parameter "fill_value" requires a space before the colon separating the parameter name and type
pandas.DataFrame.from_csv: Parameter "infer_datetime_format" requires a space before the colon separating the parameter name and type
pandas.Panel.asfreq: Parameter "fill_value" requires a space before the colon separating the parameter name and type
pandas.DatetimeIndex.to_perioddelta: Parameter "freq" requires a space before the colon separating the parameter name and type
pandas.TimedeltaIndex: Parameter "unit" requires a space before the colon separating the parameter name and type
pandas.Period.to_timestamp: Parameter "how" requires a space before the colon separating the parameter name and type
pandas.Timestamp.replace: Parameter "nanosecond" requires a space before the colon separating the parameter name and type
pandas.tseries.offsets.SemiMonthEnd: Parameter "n" requires a space before the colon separating the parameter name and type
pandas.tseries.offsets.SemiMonthEnd: Parameter "day_of_month" requires a space before the colon separating the parameter name and type
pandas.tseries.offsets.SemiMonthBegin: Parameter "n" requires a space before the colon separating the parameter name and type
pandas.tseries.offsets.SemiMonthBegin: Parameter "day_of_month" requires a space before the colon separating the parameter name and type
pandas.core.groupby.DataFrameGroupBy.boxplot: Parameter "subplots " requires a space before the colon separating the parameter name and type
pandas.core.resample.Resampler.asfreq: Parameter "fill_value" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler: Parameter "data" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler: Parameter "precision" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler: Parameter "table_styles" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler: Parameter "uuid" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler: Parameter "caption" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler: Parameter "cell_ids" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.format: Parameter "formatter" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.format: Parameter "subset" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.set_precision: Parameter "precision" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.set_table_styles: Parameter "table_styles" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.set_caption: Parameter "caption" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.set_properties: Parameter "subset" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.set_properties: Parameter "kwargs" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.set_uuid: Parameter "uuid" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.highlight_max: Parameter "subset" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.highlight_max: Parameter "color" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.highlight_max: Parameter "axis" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.highlight_min: Parameter "subset" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.highlight_min: Parameter "color" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.highlight_min: Parameter "axis" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.highlight_null: Parameter "null_color" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.background_gradient: Parameter "cmap" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.background_gradient: Parameter "low, high" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.background_gradient: Parameter "axis" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.background_gradient: Parameter "subset" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.background_gradient: Parameter "text_color_threshold" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.render: Parameter "`**kwargs`" requires a space before the colon separating the parameter name and type
pandas.io.formats.style.Styler.use: Parameter "styles" requires a space before the colon separating the parameter name and type
pandas.plotting.andrews_curves: Parameter "color" requires a space before the colon separating the parameter name and type
pandas.plotting.andrews_curves: Parameter "kwds" requires a space before the colon separating the parameter name and type
pandas.plotting.lag_plot: Parameter "series" requires a space before the colon separating the parameter name and type
pandas.plotting.lag_plot: Parameter "lag" requires a space before the colon separating the parameter name and type
pandas.plotting.lag_plot: Parameter "ax" requires a space before the colon separating the parameter name and type
pandas.plotting.lag_plot: Parameter "kwds" requires a space before the colon separating the parameter name and type
pandas.plotting.parallel_coordinates: Parameter "frame" requires a space before the colon separating the parameter name and type
pandas.plotting.parallel_coordinates: Parameter "class_column" requires a space before the colon separating the parameter name and type
pandas.plotting.parallel_coordinates: Parameter "cols" requires a space before the colon separating the parameter name and type
pandas.plotting.parallel_coordinates: Parameter "ax" requires a space before the colon separating the parameter name and type
pandas.plotting.parallel_coordinates: Parameter "color" requires a space before the colon separating the parameter name and type
pandas.plotting.parallel_coordinates: Parameter "use_columns" requires a space before the colon separating the parameter name and type
pandas.plotting.parallel_coordinates: Parameter "xticks" requires a space before the colon separating the parameter name and type
pandas.plotting.parallel_coordinates: Parameter "colormap" requires a space before the colon separating the parameter name and type
pandas.plotting.parallel_coordinates: Parameter "axvlines" requires a space before the colon separating the parameter name and type
pandas.plotting.parallel_coordinates: Parameter "axvlines_kwds" requires a space before the colon separating the parameter name and type
pandas.plotting.parallel_coordinates: Parameter "sort_labels" requires a space before the colon separating the parameter name and type
pandas.plotting.parallel_coordinates: Parameter "kwds" requires a space before the colon separating the parameter name and type
pandas.set_option: Parameter "value " requires a space before the colon separating the parameter name and type
pandas.api.types.union_categoricals: Parameter "ignore_order" requires a space before the colon separating the parameter name and type
pandas.Series.as_matrix: Parameter "columns" requires a space before the colon separating the parameter name and type
pandas.Series.from_csv: Parameter "infer_datetime_format" requires a space before the colon separating the parameter name and type
pandas.DataFrame.as_matrix: Parameter "columns" requires a space before the colon separating the parameter name and type
pandas.Panel.as_matrix: Parameter "columns" requires a space before the colon separating the parameter name and type
```

Calling the same script with the parameter `--format=azure` can be useful, as it reports also the file and the line where the function is defined. Python introspection is used to obtain them, and it probably won't be correct if the function is created dynamically, but it could be helpful in many cases. Using `grep "encoding:"` is also an option (`encoding` is the name of the parameter of the first detected failing case).

We should add all the missing spaces and fix all the formats. Executing the script after this has been done, should report no errors. 