title: pandas dataframe interpolate
body: <p>So I see that there is a way to interpolate for a pandas series object <a href="http://pandas.pydata.org/pandas-docs/dev/generated/pandas.Series.interpolate.html" rel="nofollow">http://pandas.pydata.org/pandas-docs/dev/generated/pandas.Series.interpolate.html</a>. Is there an equivalent method for dataframes? I'd like to interpolate every column.</p>