MAINT Enable flake8 for travis.
MAINT Enable flake8 for travis.

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