minor doc tweaks
minor doc tweaks

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