Fixed a bug that caused masked FITS tables to be read incorrectly. This is quite subtle because it turns out that comparing a column to None with == does not return a boolean array, but a single boolean. This then causes the first row to always be masked (since False is the same as 0).
Added regression test for #1795
Merge pull request #1795 from astrofrog/fix-fits-masking

Strange mask values for FITS table