rename 'deriv' to 'fit_deriv' in documenation
rename 'deriv' to 'fit_deriv' in documenation

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