Fixed stats_smooth.py to ensure that dataframes with NaN values are rendered correctly.  Proir to this fix, no fit line was drawn when using the 'lm' method.
Fixed stats_smooth.py to ensure that dataframes with NaN values are rendered correctly.  Proir to this fix, no fit line was drawn when using the 'lm' method.

yhat/ggplot,yhat/ggplot