ENH Add label for percentiles.
ENH Add label for percentiles.

yanheven/pyfolio,sketchytechky/pyfolio,yanheven/pyfolio,dursk/pyfolio,quantopian/pyfolio,raybuhr/pyfolio,r0k3/pyfolio,quantopian/pyfolio,chayapan/pyfolio,r0k3/pyfolio,sketchytechky/pyfolio,dursk/pyfolio,femtotrader/pyfolio,ChinaQuants/pyfolio,YihaoLu/pyfolio,ChinaQuants/pyfolio,raybuhr/pyfolio,YihaoLu/pyfolio,femtotrader/pyfolio