Fixes #725. Moved the cython_version.py generation until after the normal build_ext command runs.  There was really no specific reason for it to go first.  Also check to ensure that the build/lib directory exists yet before doing anything with it.
Add initial infrastructure for io.ascii meta handling
Update DAOphot reader to use new meta infrastructure
Parse IPAC table metadata (keywords and comments)
Fix mistake in IPAC reader docstring
Improve DAOphot and IPAC reader docstrings
Improve the CDS reader doc string regarding metadata
Update IPAC docstring to fix an error in sphinx build
Make IPAC and DAOphot examples work literally and show output
When downloading a file, and we know it's size from the header, check that the temp filesystem and, if necessary, the cache filesystem have enough space before beginning the download.
Add SI prefixes to arcsecond
Get a better error message when conflicting units are defined.
Delete the temporary file if a download fails or is interrupted
Fix #863, that degree is not a base in SI
Add TimeAstropyTime format to instantiate from list of Times
Merge pull request #858 from mdboom/utils/check-file-size-before-download

Check free space before downloading a file
Merge pull request #876 from mdboom/unit/arcsec-prefixes

Units: SI prefixes for angular units
Merge pull request #863 from mdboom/unit/dont_compose_to_degrees

units: use "radian" for si/cgs units for angle?
Merge pull request #857 from mdboom/utils/delete-file-when-download-fails

Delete the temporary file if a download fails or is interrupted
Use scale of first item when initing from list of Times