Added ability to override config file (e.g. for tests).
Added ability to override config file (e.g. for tests).

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