Expanded 'Using astropy.test()' section and added a link on test discovery rules to to the 'Writing tests' section.
Expanded 'Using astropy.test()' section and added a link on test discovery rules to to the 'Writing tests' section.

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