added test_imports to make sure all packages successfully import
added open_api_page function
Initial version of the astropy.constants docs
Add equivalency for f_nu <-> nu * f_nu
Add equivalency for f_lambda <-> lambda * f_lambda
include all cosmology functions as methods of the cosmology object
remove now-incorrect sentence from cosmology docs
Added a section on using setup.py develop.  This will provide a good segue into talking about virtualenv. Will also add the suggested docs for trying out a PR
Added a basic overview of using virtualenv
Add some notes on virtualenvwrapper and venv; fix some minor sphinx syntax issues
Here are some additional notes on using virtualenv with IPython
This is a mostly trivial change, but it's also more consistent--if the other unit conversions in this class are using abbreviations why shouldn't lightyear? Alternatively, both versions could be made available (i.e 'lightyear' and 'lyr', likewise 'pc' and 'parsec', etc.)
Got rid of references to './setup.py' per @astrofrog's comments. I still used to just 'setup.py foo' when referencing specific setup.py commands, but wrote out 'python setup.py' when discussing full commands run at the command line.
Update astropy.time setup to allow using system sofa_c library
Related to #618, this adds a What's New section for units and quantities.
As per #618, adds a "What's New in 0.2" section for `io.votable`.
As per #618, adds a "What's New in 0.2" section for `wcs`
Added long-form and short-form versions of all the unit conversions.  Also added 'redshift' as a long-form for 'z'.  Not sure if that's really necessary though since I think 'z' is pretty well understood.  I'm also not sure how I feel about spelling out 'astronomical_units' but I put it in for completeness.
Correct typo
Fix failing hdf5 tests.

Some of these tests were failing for me for a while--I figured it was a problem with my h5py installation but upon closer inspection it seemed to be a problem more with the tests and Unicode issues.

I don't know why these weren't caught sooner except that maybe most of the test bots don't have h5py installed.

This fixes the tests for now but there are some broader issues that need a look involving Unicode support.  Currently h5py does not support numpy 'U' arrays, though it has no problem taking utf8-encoded bytestrings.  So we might have implement some sort of hack to loop through table columns and convert any unicode arrays to byte arrays before shoving them into the hdf5 dataset.