Merge pull request #2776 from joergdietrich/omega_b

Add baryonic matter density paramter and its evolution to cosmology classes
Update astropy_helpers submodule to the commit to be tagged astropy-helpers v0.4.2
Removed trailing space
Add API changes section about VOUnit changes.
Added calls to super() in fast reading __init__ methods
Merge pull request #2901 from mdboom/unit/vounit-10-update

Support version 1.0 of the VOUnit standard
Add bit/byte equivalency
Merge pull request #2925 from mdboom/unit/bit-byte-nibble

Implement bit-byte unit equivalency and nibble unit
Update astropy_helpers submodule to the commit to be tagged astropy-helpers v0.4.2
Merge pull request #2924 from embray/ah-update

Test astropy-helpers for v0.4.2 release
Merge pull request #2893 from migueldvb/docs

Documentation fixes
Change bullets in affiliated package instructions to numbers
Update index.rst
Merge pull request #2912 from astrofrog/affiliated-release

Added affiliated package release instructions
Mentioned that fast suboptions are false by default in a couple other places
Merge pull request #2716 from amras1/fast-c-reader

Added a new fast reading/writing engine to io.ascii
Fix typo in io.ascii read.rst [skip ci]
use suggestion from @astrofrog
Should fix #2794 and a related issue (in that the replaced code had this bug as well) with writing non-contiguous arrays to non-file objects.
Fix mistake in chunksize calculation