Fixes issue raising some VO warnings when DeprecationWarnings are
converted to exceptions on Python 2.6
Fix rebuilding col views where parent table was not set
Update CHANGES.rst with #2039 fix
Fixed pragma typo in _open_shelve
Merge pull request #2039 from taldcroft/table/rebuild-cols

Can't rename table columns after sorting
Don't do the _tempfilestodel check if it is None

Closes #2036
Merge pull request #2043 from eteq/fix-2036

Fix for #2036
Merge pull request #2027 from mdboom/vo/exception-deprecation

Fix deprecation on Python 2.6 when raising some warnings in `io.votable`
Merge pull request #2042 from pllim/fix-shelve-pragma

Fixed pragma typo in _open_shelve
Disabled 2to3 and use six for astropy.vo instead.
Applied review comments.