Make Row, Column, MaskedColumn, TableColumns be class attributes
Add initial tests of subclassing components
Make the user-subclassable attributes be public (no _)
Refactor pprint funcs into class to allow formatting customization
Make subclass testing more boring
Add subclassed Table into test fixture for broad testing
Add docs on subclassing
Update CHANGES.rst
Add top-level reference to subclassing, fix doc problems
Change t.pprint() to print(t) to fix doctest errs on Mac
Fix RST docs to run correctly and be more clear
Fixes for remote-data tests prior to APE3 work.
Change allocation in WCS.sub.

Conflicts:
	astropy/wcs/src/wcslib_wrap.c
Add CHANGES entry.
Don't display configuration deprecation warning messages within
`setup.py test`.  Improve warning messages about deprecated
configuration items.
fix for deprecated self.naxis1/2
Restore new config code lost in rebase
Merge pull request #2287 from taldcroft/subclass-table

Subclass Table components Row, Column, etc
Added dV_comoving function and tests.

The dV_comoving function allows for an easy method of integrating
over a comoving volume. It is useful when, for example,
integrating a function that depends on another function whose
sensitivity changes with redshift.
Renamed function to differential_comoving_volume

Changed relevant doc_strings and tests as well. As discussed at
https://github.com/astropy/astropy/pull/2103.