Fix Database.query with the Time attribute.
This fixes #771.
Merge branch 'master' of https://github.com/sunpy/sunpy into issue771
Merge branch 'master' of https://github.com/sunpy/sunpy into issue771
updates tests from test_attrs.py to latest changes
Merge pull request #780 from derdon/issue771

Fix vso.attrs.Time for querying databases