Working fix for unsigned int conversions
Convert print statement to warning
All uint tests now working
missing colon
parametrize test and other minor changes
Also parametrize uint image tests
fully parametrize uint tests
Fix different hdu number in compressed files.  Also, closes #362 and closes #880
Disable test of 64-bit compressed image
add placeholder for uint parameter
Fix bad except statement
Fix test parameter
Restructure test parameters
Change the way column attributes are assigned
Changed some of the wording in units docs to clarify what "unit formats" is about
added more subsections and generified base formats.rst title
Changed format.rst section title to @mdboom's suggestion

[ci skip]
Changed section title form "Units" to "Units and Quantities"

[ci skip]
Reallow comparison with 0 even for dimensional quantities
And also treat inf and nan as quantities that can have arbitrary units