Document why the test fixtures are defined in conftest.py
Document why the test fixtures are defined in conftest.py

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