Fix validation error type `SS03` and check in CI
#### Problem description
In order to have a continuous check by the CI on validation error `SS03` (Summary does not end with a period), fixing them in the code base enables the addition to the CI for automated testing in the future.

`SS03` has 178 occurrences (see [overview of the errors](https://gist.github.com/198cfa552c727d71bd7360fda66fdbb4)), including:

method | file | file_line | github_link
-- | -- | -- | -- |
pandas.Timestamp | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.max | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.min | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.resolution | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.tz | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.ceil | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.combine | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.floor | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.fromordinal | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.isoweekday | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.replace | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.round | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.to_datetime64 | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.weekday | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.components | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.view | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.ceil | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.floor | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.isoformat | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.round | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.to_pytimedelta | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.to_timedelta64 | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.total_seconds | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Period | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Period.asfreq | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Period.strftime | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Period.to_timestamp | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Interval.closed | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Interval.left | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Interval.length | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
... | ... | ... | ...
pandas.tseries.offsets.CBMonthEnd.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.CBMonthBegin.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.CDay.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.frequencies.to_offset | pandas/tseries/frequencies.py | 59.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/tseries/frequencies.py#L59
pandas.Panel.axes | pandas/core/generic.py | 441.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L441
pandas.Panel.shape | pandas/core/generic.py | 434.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L434
pandas.Panel.__iter__ | pandas/core/generic.py | 1819.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L1819
pandas.Panel.iteritems | pandas/core/generic.py | 1832.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L1832
pandas.Panel.lt | pandas/core/ops.py | 2170.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/ops.py#L2170
pandas.Panel.gt | pandas/core/ops.py | 2170.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/ops.py#L2170
pandas.Panel.le | pandas/core/ops.py | 2170.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/ops.py#L2170
pandas.Panel.ge | pandas/core/ops.py | 2170.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/ops.py#L2170
pandas.Panel.ne | pandas/core/ops.py | 2170.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/ops.py#L2170
pandas.Panel.eq | pandas/core/ops.py | 2170.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/ops.py#L2170
pandas.Panel.swaplevel | pandas/core/generic.py | 932.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L932
pandas.Panel.transpose | pandas/core/panel.py | 1269.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/panel.py#L1269
pandas.plotting.deregister_matplotlib_converters | pandas/plotting/_converter.py | 88.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/plotting/_converter.py#L88
pandas.plotting.register_matplotlib_converters | pandas/plotting/_converter.py | 55.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/plotting/_converter.py#L55
pandas.core.resample.Resampler.first | pandas/core/resample.py | 857.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/resample.py#L857
pandas.core.resample.Resampler.last | pandas/core/resample.py | 857.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/resample.py#L857
pandas.core.resample.Resampler.max | pandas/core/resample.py | 857.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/resample.py#L857
pandas.core.resample.Resampler.min | pandas/core/resample.py | 857.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/resample.py#L857
pandas.core.resample.Resampler.prod | pandas/core/resample.py | 846.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/resample.py#L846
pandas.core.resample.Resampler.sum | pandas/core/resample.py | 846.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/resample.py#L846
pandas.io.formats.style.Styler.loader | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.io.formats.style.Styler.set_caption | pandas/io/formats/style.py | 778.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/io/formats/style.py#L778
pandas.Panel.items | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Panel.keys | pandas/core/generic.py | 1824.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/core/generic.py#L1824
pandas.Panel.major_axis | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Panel.minor_axis | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone


Todo:

* [ ]     get rid of the errors in the code base
* [ ]     update the `code_check.sh` script to take into account the `SS03` type of errors