Added Beta models
Added Beta models

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