Add pull request number to changelog.
Add pull request number to changelog.

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