Change sin & cos tests to testcases.
Change sin & cos tests to testcases.

Eventually as many tests as possible in this file will be changed
to use 'testcases' which tests a quantity input against a quantity
output for a given function in a more readable and easily maintained
way.

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