Add `_get_numeric_data()` to the public API?
In a [tool that I'm building](https://github.com/jackmaney/ucc-pandas) that utilizes Pandas data frames, I'm adding a simple data validation layer to only accept numeric columns of a given data frame. I found a [Stack Overflow question](http://stackoverflow.com/questions/12725417/drop-non-numeric-columns-from-a-pandas-dataframe) from a bit over a year ago pointing out the private `_get_numeric_data()` method in the `DataFrame` class. Would it be possible to make this method part of the public API?

(And my apologies if this request has been made before; I did a few searches through the issues and didn't find anything.)
