Fix missing space around : for sphinx docs.  Add Flatw0waCDM.
Fix missing space around : for sphinx docs.  Add Flatw0waCDM.

It turns out sphinx binds the documentation incorrectly
if there is not a space on both sides of : in things like
z : ndarray.  So, fixed.

Added trivial Flatw0waCDM cosmology class.

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