Speed up distance calculations by ~10x.  Only done for FlatLambdaCDM.
Speed up distance calculations by ~10x.  Only done for FlatLambdaCDM.

* Break out some internal functions for the integrators to call
  directly
* Tests pass, distances are about 10x faster than before, now
  about 5x faster than cosmolopy.

This is only done for a) distances, b) FlatLambdaCDM.  The idea
is to show exactly how ugly this solution is so we can decide
if it's worth implementing for the other cosmologies.  Sure
does speed things up though...

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