update changelog for 1.1 release
update changelog for 1.1 release

[ci skip]

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