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.
An alternative to the fix in #634. This forces the use of Distribute so that
we don't generally have to worry about supporting Setuptools.  This is Good
because although Setuptools and Distribute are both a mess, the latter fixes
several bugs that remain unfixed in the former, and includes features we rely
on such as 2to3 which are not backwards compatible with Setuptools.

The fix in #634 is slightly misleading because simply calling
`import setuptools` does not, in all cases, imply that the "system distribute"
is being used.  The "system distribute" is in fact not well-defined because it
depends on knowing the default installation path for Python packages on the
particular OS in use.

This approach simply checks to see if there's already a Distribute installation
on the Python path and forces it to be used over Setuptools if a potential
conflict exists between them.  It only uses disribute_setup if no version of
Distribute is available at all.
Use imp.reload instead of relying on the reload() builtin.
Add note to changelog about this pull request.
Fix cosmology documents to give default cosmology correctly.
for github/astropy#557
implemented comments from @iguananaut
attempt to fix failed travis build for Python 3.2 based on @mdboom suggestion
unittest.skipIf not available until Python 3.1, trying pytest skip
Added unary operators for Quantity
Added abs operator for Quantity
Merge pull request #640 from iguananaut/use-distribute

An alternative to the fix in #634, #630, etc.
Merge pull request #629 from aconley/wmap9 (with manual merge)
Merge pull request #644 from astrofrog/unit/unary-operators-quantity

Added unary operators for Quantity
Merge pull request #643 from pllim/compat-futures

Add concurrent.futures to astropy.utils.compat
Merge branch 'master' into vo-conesearch
updated async conesearch to use  from astropy#643