DataFrame.hist does not honor sharex or sharey set to True
[Here is an example](http://nbviewer.ipython.org/urls/gist.github.com/fonnesbeck/5897459/raw/6181f066f245c7fb489b68f88e4b4731c77a238b/King%27s+Bay+Survey+Analysis.ipynb) of the `hist` method called as a multi-panel plot via the `by` argument, with `sharey=True` and `sharex=True`. As you can observe in the plot at the bottom of the notebook, neither the x nor the y axis is shared among the subplots.

Running 0.11.1 on Python 2.7.2 (OS X 10.8.4).
