add guideline on useful information
add guideline on useful information

aleksandr-bakanov/astropy,lpsinger/astropy,stargaser/astropy,dhomeier/astropy,mhvk/astropy,saimn/astropy,lpsinger/astropy,mhvk/astropy,mhvk/astropy,MSeifert04/astropy,saimn/astropy,saimn/astropy,bsipocz/astropy,StuartLittlefair/astropy,astropy/astropy,StuartLittlefair/astropy,stargaser/astropy,StuartLittlefair/astropy,mhvk/astropy,lpsinger/astropy,lpsinger/astropy,saimn/astropy,bsipocz/astropy,bsipocz/astropy,mhvk/astropy,StuartLittlefair/astropy,pllim/astropy,larrybradley/astropy,larrybradley/astropy,larrybradley/astropy,saimn/astropy,astropy/astropy,aleksandr-bakanov/astropy,dhomeier/astropy,MSeifert04/astropy,StuartLittlefair/astropy,pllim/astropy,bsipocz/astropy,dhomeier/astropy,pllim/astropy,aleksandr-bakanov/astropy,pllim/astropy,astropy/astropy,lpsinger/astropy,MSeifert04/astropy,dhomeier/astropy,astropy/astropy,MSeifert04/astropy,pllim/astropy,larrybradley/astropy,stargaser/astropy,larrybradley/astropy,dhomeier/astropy,stargaser/astropy,astropy/astropy,aleksandr-bakanov/astropy