DataFrame.plot docstring missing a few parameters
Looking at the [plot accessor docstring][1], it's missing 

* `ax`
* `subplots`
* `sharex`
* `sharey`
* `secondary_y`
* `sort_columns`

Maybe others.

Also would be nice to have documentation of all parameters for all the accessor methods i.e. `df.plot.bar`.


[1]: https://github.com/pandas-dev/pandas/blob/master/pandas/plotting/_core.py#L579