Add another reference to virtual environment documentation
Add another reference to virtual environment documentation

joergdietrich/astropy,larrybradley/astropy,larrybradley/astropy,dhomeier/astropy,StuartLittlefair/astropy,larrybradley/astropy,MSeifert04/astropy,AustereCuriosity/astropy,stargaser/astropy,bsipocz/astropy,funbaker/astropy,saimn/astropy,saimn/astropy,astropy/astropy,AustereCuriosity/astropy,lpsinger/astropy,MSeifert04/astropy,kelle/astropy,AustereCuriosity/astropy,DougBurke/astropy,funbaker/astropy,stargaser/astropy,dhomeier/astropy,stargaser/astropy,pllim/astropy,bsipocz/astropy,bsipocz/astropy,aleksandr-bakanov/astropy,dhomeier/astropy,lpsinger/astropy,AustereCuriosity/astropy,funbaker/astropy,pllim/astropy,tbabej/astropy,bsipocz/astropy,joergdietrich/astropy,kelle/astropy,pllim/astropy,dhomeier/astropy,DougBurke/astropy,joergdietrich/astropy,StuartLittlefair/astropy,mhvk/astropy,kelle/astropy,larrybradley/astropy,DougBurke/astropy,lpsinger/astropy,mhvk/astropy,tbabej/astropy,astropy/astropy,tbabej/astropy,aleksandr-bakanov/astropy,lpsinger/astropy,mhvk/astropy,saimn/astropy,joergdietrich/astropy,kelle/astropy,mhvk/astropy,mhvk/astropy,astropy/astropy,MSeifert04/astropy,StuartLittlefair/astropy,larrybradley/astropy,kelle/astropy,AustereCuriosity/astropy,tbabej/astropy,dhomeier/astropy,joergdietrich/astropy,stargaser/astropy,saimn/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,StuartLittlefair/astropy,saimn/astropy,pllim/astropy,DougBurke/astropy,tbabej/astropy,funbaker/astropy,astropy/astropy,lpsinger/astropy,astropy/astropy,pllim/astropy,MSeifert04/astropy,aleksandr-bakanov/astropy