Add regression equivalency test for all PA, separation methods.
Add regression equivalency test for all PA, separation methods.

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