add YAML serialization to what's new in 1.3
add YAML serialization to what's new in 1.3

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