change units to unit in all Table and Column objects
update docs with unit change
add deprecated units property
add setter and deleter deprecation
gotta call deprecated with arguments...
change dtypes to dtype
change dtypes to dtype in tests
adding back plural kwargs with warnings
deprecated_attribute doesn't do what we want, switch back to deprecated() on getter, setter, deleter...
add test to make sure .units works, and issues a DeprecationWarning
tests for deprecated attributes
deprecated .dtypes attribute and test for warning
add dtypes kwarg to Table, with warning
fixing test failures
Fix failing tests..how did these sneak through?
fix test in io.fits that used Column.units
update changelog to reflect modifications
fix indentation error
units to unit in table index doc
more units to unit changes in docs...oops