Added a note discouraging the use of multiple inheritance, and added an example of using a mixin class
Added a note discouraging the use of multiple inheritance, and added an example of using a mixin class

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