Add support for OGIP format units.
Add warning that `Wcsprm` should not be used to get the original values
of keywords in the header.
Call `set` from within the WCS constructor.
Add convenience class for comma-separated-values files

Read and write comma-separated-values files with
ascii.read(‘file.csv’,format=‘csv’)
ascii.write(table,”output.csv”,format=‘csv’)
Does not yet automatically recognize .csv extension
Add tests for CSV in io.ascii
Add CSV test file
Up Time's __array_priority__ to above Quantity's
Merge pull request #1940 from mhvk/time-array-priority

Up Time's __array_priority__ to above Quantity's
Add CSV option to documentation tables
Fixed bugs in sphinx docs
Add Table/Unified interface tests for CSV files
Don't call did you mean unless the exception is expected to bubble up to the user
Set detailed_exception to False from within the CDS parse function as well.
Update CHANGES.rst

These changelog entries were in the wrong section, as confirmed by Marten.
Merge pull request #1933 from mdboom/unit/less-did-you-mean

Creating TimeDeltas is now extremely slow
Merge pull request #1918 from mdboom/wcs/wcsprm-members

WCS changes velocity units from km/s to m/s
Accept multiple slashes in unit strings.
Accept "angstrom" (lower-case a) as a deprecated unit in FITS
Skip some doctests, since we can't reliably always get a warning out.
Fix doctest for upstream change.