Updated docstring.
Updated docstring.

jchodera/pymbar,mrshirts/pymbar,wesbarnett/pymbar,kyleabeauchamp/pymbar,Lnaden/pymbar,jchodera/pymbar,Lnaden/pymbar,wesbarnett/pymbar,kyleabeauchamp/pymbar,mrshirts/pymbar,wesbarnett/pymbar,choderalab/pymbar,Lnaden/pymbar,kyleabeauchamp/pymbar,kyleabeauchamp/pymbar,choderalab/pymbar,mrshirts/pymbar,jchodera/pymbar,choderalab/pymbar,mrshirts/pymbar,jchodera/pymbar,wesbarnett/pymbar