BUG Remove stray usage of correlation measure.
BUG Remove stray usage of correlation measure.

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