STY PEP8 Fixes for plotting.py
STY PEP8 Fixes for plotting.py

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