write only relative path in 'RECORD'
write only relative path in 'RECORD'

RECORD now contains only relative path.
some bugs triggered by a bleeding edge usage of python may disappear a result (https://github.com/pypa/pip/issues/3433)
mindw/pip,zvezdan/pip,natefoo/pip,pypa/pip,pradyunsg/pip,rouge8/pip,sigmavirus24/pip,zvezdan/pip,fiber-space/pip,fiber-space/pip,rouge8/pip,rouge8/pip,xavfernandez/pip,techtonik/pip,pfmoore/pip,mindw/pip,sbidoul/pip,benesch/pip,sbidoul/pip,techtonik/pip,atdaemon/pip,nthall/pip,atdaemon/pip,pradyunsg/pip,xavfernandez/pip,benesch/pip,sigmavirus24/pip,zvezdan/pip,atdaemon/pip,sigmavirus24/pip,fiber-space/pip,pfmoore/pip,benesch/pip,xavfernandez/pip,techtonik/pip,RonnyPfannschmidt/pip,RonnyPfannschmidt/pip,natefoo/pip,dstufft/pip,nthall/pip,dstufft/pip,RonnyPfannschmidt/pip,mindw/pip,nthall/pip,pypa/pip,dstufft/pip,natefoo/pip