API: consider deprecating DataFrame.hist in favor of DataFrame.plot.hist
This came up in the PR adding plot submethods like `.plot.hist`:  https://github.com/pydata/pandas/pull/9321#issuecomment-139203762

As long as API differences can be reconciled, I think it would be a nice idea to deprecate (and eventually remove) `DataFrame.hist`, `DataFrame.boxplot` and `Series.hist` in favor of the accessor mtehods.

This old issue discusses API differences (possibly no longer accurate/relevant?): https://github.com/pydata/pandas/issues/413
