Add tests of setting of representations.
Add tests of setting of representations.

Including of different types.

lpsinger/astropy,lpsinger/astropy,mhvk/astropy,StuartLittlefair/astropy,astropy/astropy,aleksandr-bakanov/astropy,dhomeier/astropy,larrybradley/astropy,pllim/astropy,aleksandr-bakanov/astropy,pllim/astropy,StuartLittlefair/astropy,pllim/astropy,larrybradley/astropy,larrybradley/astropy,astropy/astropy,StuartLittlefair/astropy,saimn/astropy,lpsinger/astropy,larrybradley/astropy,astropy/astropy,saimn/astropy,pllim/astropy,StuartLittlefair/astropy,dhomeier/astropy,dhomeier/astropy,dhomeier/astropy,saimn/astropy,larrybradley/astropy,saimn/astropy,saimn/astropy,pllim/astropy,mhvk/astropy,lpsinger/astropy,mhvk/astropy,astropy/astropy,dhomeier/astropy,mhvk/astropy,aleksandr-bakanov/astropy,astropy/astropy,mhvk/astropy,lpsinger/astropy,StuartLittlefair/astropy,aleksandr-bakanov/astropy