Added some documentation for running the tests with tox
Added some documentation for running the tests with tox

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