Add __repr__ to InstallRequirement
Add __repr__ to InstallRequirement

This makes it easier to inspect with pdb.

Instead of:

    (Pdb++) req_to_install
    <pip.req.req_install.InstallRequirement object at 0x10459f7d0>

we get the much friendlier:

    (Pdb++) req_to_install
    <InstallRequirement object: wheel==0.24.0 in /Users/marca/python/virtualenvs/pip/lib/python2.7/site-packages>

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