Default ``data_start`` to 0 in ``CommentedHeader``

fixes #2692
Made Latex/AASTex tables use unit attribute of Column for output
Provide np.broadcast_arrays replacement that allows subclasses
Determine whether to overload by testing for the actual problem
Add numpy license
Move from astropy.utils to astropy.utils.compat
Add documentation, and make things confirm to it
Do not import test function in compat.numpy; associated changes
Use final numpy version, use it in coordinates, add changelog entry
Only import what's necessary, slight modification of instructions.
quantity: remove space if unitless quantity
consolidate unitstr into property
fix doctests for dimensionless format call
add changelog entry
remove repr test
Add missing CHANGELOG entry for #2816
Merge pull request #3103 from mdboom/add-missing-changelog-entry

Add missing CHANGELOG entry for #2816
Support Pythons without bz2 support
Simplified units logic and updated test
Merge pull request #3097 from zblz/fix-print-unitless

Quantity: remove trailing space if quantity has no units