Pandas DataFrame.plot() does not default to matplotlib rcparams grid setting
When using df.plot() to creat a simple line chart from a dataframe, the expected behavior is that, if no 'grid' keyword is passed, the plot will default to the matplotlib 'axes.grid' rcParam setting to determine whether to show a grid or not.  However (in 0.16), the grid is always being shown, regardless of the matplotlib setting, unless I explicitly pass grid=False.

In general, there are several plot types where grid=True is forced, which basically breaks the consistent styling that you get from matplotlib rcparams or another package like Seaborn.  I can understand forcing a default grid=False for the type of plots where a grid doesn't make sense, but forcing grid=True, overriding the configured defaults, for things like boxplots seems a bit counter intuitive.
