Added linkcheck feature to circleCI
Added linkcheck feature to circleCI

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