BLD: Lazy-load Cython and numpy when installing package.
BLD: Lazy-load Cython and numpy when installing package.

Modify setup.py to defer the use of Cython and numpy until
`setup_requires` has already been processed, so that Cython and numpy
are available when they are needed.

ChinaQuants/zipline,wilsonkichoi/zipline,michaeljohnbennett/zipline,aajtodd/zipline,chrjxj/zipline,grundgruen/zipline,quantopian/zipline,florentchandelier/zipline,umuzungu/zipline,otmaneJai/Zipline,grundgruen/zipline,dmitriz/zipline,CDSFinance/zipline,magne-max/zipline-ja,gwulfs/zipline,MonoCloud/zipline,wilsonkichoi/zipline,alphaBenj/zipline,sketchytechky/zipline,DVegaCapital/zipline,kmather73/zipline,nborggren/zipline,wubr2000/zipline,MonoCloud/zipline,quantopian/zipline,morrisonwudi/zipline,nborggren/zipline,humdings/zipline,morrisonwudi/zipline,zhoulingjun/zipline,ChinaQuants/zipline,sketchytechky/zipline,DVegaCapital/zipline,umuzungu/zipline,jimgoo/zipline-fork,dkushner/zipline,bartosh/zipline,YuepengGuo/zipline,kmather73/zipline,alphaBenj/zipline,dmitriz/zipline,dkushner/zipline,humdings/zipline,joequant/zipline,aajtodd/zipline,wubr2000/zipline,florentchandelier/zipline,cmorgan/zipline,cmorgan/zipline,enigmampc/catalyst,zhoulingjun/zipline,Scapogo/zipline,gwulfs/zipline,enigmampc/catalyst,jimgoo/zipline-fork,magne-max/zipline-ja,Scapogo/zipline,chrjxj/zipline,michaeljohnbennett/zipline,CDSFinance/zipline,YuepengGuo/zipline,otmaneJai/Zipline,joequant/zipline,bartosh/zipline