MAINT: Use DatetimeIndex instead of OrderedDict for trading days.
MAINT: Use DatetimeIndex instead of OrderedDict for trading days.

Looking forwards to Python 3 capability, maintaing code that uses
iterkeys would require some overhead of checking what Python version
is available etc., instead use a DatetimeIndex so there is no need
to use key iterators, reverse, etc. on an OrderedDict, as the
DatetimeIndex allows 0 and -1 index, as well as the needed fast `in`
functionality.

gwulfs/zipline,erikness/AlephOne,jimgoo/zipline-fork,zhoulingjun/zipline,michaeljohnbennett/zipline,joequant/zipline,kmather73/zipline,otmaneJai/Zipline,wilsonkichoi/zipline,StratsOn/zipline,quantopian/zipline,morrisonwudi/zipline,wubr2000/zipline,semio/zipline,umuzungu/zipline,euri10/zipline,dkushner/zipline,sketchytechky/zipline,otmaneJai/Zipline,erikness/AlephOne,bartosh/zipline,DVegaCapital/zipline,CarterBain/AlephNull,stkubr/zipline,CDSFinance/zipline,YuepengGuo/zipline,quantopian/zipline,euri10/zipline,iamkingmaker/zipline,semio/zipline,davidastephens/zipline,dmitriz/zipline,dmitriz/zipline,aajtodd/zipline,AlirezaShahabi/zipline,bartosh/zipline,cmorgan/zipline,CarterBain/AlephNull,kmather73/zipline,florentchandelier/zipline,iamkingmaker/zipline,keir-rex/zipline,jordancheah/zipline,morrisonwudi/zipline,enigmampc/catalyst,humdings/zipline,humdings/zipline,ChinaQuants/zipline,davidastephens/zipline,mattcaldwell/zipline,aajtodd/zipline,florentchandelier/zipline,umuzungu/zipline,magne-max/zipline-ja,dhruvparamhans/zipline,joequant/zipline,magne-max/zipline-ja,alphaBenj/zipline,chrjxj/zipline,jimgoo/zipline-fork,enigmampc/catalyst,CDSFinance/zipline,jordancheah/zipline,stkubr/zipline,ronalcc/zipline,wubr2000/zipline,grundgruen/zipline,DVegaCapital/zipline,Scapogo/zipline,cmorgan/zipline,zhoulingjun/zipline,nborggren/zipline,grundgruen/zipline,MonoCloud/zipline,dhruvparamhans/zipline,keir-rex/zipline,dkushner/zipline,MonoCloud/zipline,michaeljohnbennett/zipline,gwulfs/zipline,AlirezaShahabi/zipline,StratsOn/zipline,mattcaldwell/zipline,nborggren/zipline,wilsonkichoi/zipline,ChinaQuants/zipline,chrjxj/zipline,alphaBenj/zipline,ronalcc/zipline,Scapogo/zipline,YuepengGuo/zipline,sketchytechky/zipline