Updated ConfigOptionParser to use both config file and environmental variables.
Updated ConfigOptionParser to use both config file and environmental variables.

alex/pip,cjerdonek/pip,Gabriel439/pip,willingc/pip,haridsv/pip,prasaianooz/pip,tdsmith/pip,sigmavirus24/pip,luzfcb/pip,chaoallsome/pip,blarghmatey/pip,ncoghlan/pip,willingc/pip,zvezdan/pip,nthall/pip,pypa/pip,yati-sagade/pip,natefoo/pip,erikrose/pip,James-Firth/pip,habnabit/pip,graingert/pip,davidovich/pip,wkeyword/pip,xavfernandez/pip,alex/pip,James-Firth/pip,graingert/pip,zorosteven/pip,yati-sagade/pip,prasaianooz/pip,mindw/pip,jamezpolley/pip,haridsv/pip,wkeyword/pip,sbidoul/pip,patricklaw/pip,pradyunsg/pip,RonnyPfannschmidt/pip,pjdelport/pip,zenlambda/pip,wkeyword/pip,alquerci/pip,atdaemon/pip,alex/pip,qbdsoft/pip,jmagnusson/pip,esc/pip,qbdsoft/pip,supriyantomaftuh/pip,natefoo/pip,qbdsoft/pip,esc/pip,zorosteven/pip,graingert/pip,tdsmith/pip,ianw/pip,squidsoup/pip,mattrobenolt/pip,pfmoore/pip,squidsoup/pip,ChristopherHogan/pip,davidovich/pip,sigmavirus24/pip,KarelJakubec/pip,mujiansu/pip,James-Firth/pip,minrk/pip,zenlambda/pip,fiber-space/pip,jasonkying/pip,fiber-space/pip,jasonkying/pip,ChristopherHogan/pip,caosmo/pip,qwcode/pip,prasaianooz/pip,h4ck3rm1k3/pip,minrk/pip,jmagnusson/pip,erikrose/pip,harrisonfeng/pip,msabramo/pip,esc/pip,atdaemon/pip,chaoallsome/pip,zenlambda/pip,benesch/pip,supriyantomaftuh/pip,blarghmatey/pip,sigmavirus24/pip,rouge8/pip,jythontools/pip,squidsoup/pip,rbtcollins/pip,msabramo/pip,nthall/pip,techtonik/pip,h4ck3rm1k3/pip,mujiansu/pip,tdsmith/pip,pjdelport/pip,dstufft/pip,Gabriel439/pip,Ivoz/pip,zvezdan/pip,atdaemon/pip,zorosteven/pip,chaoallsome/pip,zvezdan/pip,nthall/pip,haridsv/pip,jamezpolley/pip,fiber-space/pip,habnabit/pip,KarelJakubec/pip,dstufft/pip,natefoo/pip,pradyunsg/pip,cjerdonek/pip,ncoghlan/pip,davidovich/pip,caosmo/pip,mujiansu/pip,jythontools/pip,ChristopherHogan/pip,benesch/pip,luzfcb/pip,yati-sagade/pip,harrisonfeng/pip,Gabriel439/pip,rouge8/pip,dstufft/pip,rbtcollins/pip,xavfernandez/pip,blarghmatey/pip,willingc/pip,caosmo/pip,xavfernandez/pip,techtonik/pip,pfmoore/pip,supriyantomaftuh/pip,Ivoz/pip,h4ck3rm1k3/pip,alquerci/pip,radiosilence/pip,jythontools/pip,pjdelport/pip,KarelJakubec/pip,harrisonfeng/pip,jasonkying/pip,ianw/pip,habnabit/pip,luzfcb/pip,mattrobenolt/pip,mindw/pip,pypa/pip,sbidoul/pip,jmagnusson/pip,ncoghlan/pip,erikrose/pip,benesch/pip,techtonik/pip,qwcode/pip,RonnyPfannschmidt/pip,jamezpolley/pip,domenkozar/pip,mindw/pip,Carreau/pip,rbtcollins/pip,Carreau/pip,RonnyPfannschmidt/pip,patricklaw/pip,rouge8/pip