Add test for Om0=1.5 Flat Universe.
Add test for Om0=1.5 Flat Universe.

Various analytic solutions fail for Om0>1.
Ensure we get still get this case right.

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