Add WMAP9 cosmology.

* Add 9 year WMAP cosmology from Hinshaw et al. 2012 (arXiv 1212.5226).
* Because this paper is on arXiv and not yet refereed/published, leave
  WMAP7 as the default.
* Add a WMAP9 test to get_current in test.
Minor fix to parameter values

* Previously, Oc0 was Oc h^2 / h^2, but table 4 actually gives
  Oc0 directly, and it's slightly different.  This is presumably
  due to the vagaries of the actual distributions for h and Oc0 h^2.
Add missing ) in source for WMAP9 cosmology.
Add note to changelog about this pull request.
Fix cosmology documents to give default cosmology correctly.
Merge pull request #629 from aconley/wmap9 (with manual merge)