Grid=True option in plot functions overrides user settings
The plotting functions on DataFrames always have grid=True. This overrides user settings in matplotlibrc.

If you have to created a desired default plot style with the rc file, you want every plot to show with this style unless otherwise specified.
Because pandas overrides this setting you have to manually set the grid option every time.

A better behaviour would be for Pandas not to override any plot styles by default.
