Implemented derdon's request for NotImplementedError.
Used a frozenset to store VSO attributes currently supported.
Fixed indentation; some weird issue with gedit
Fixed indentation again; used vim instead
Made changes according to derdon's suggestions.

1. Changed name of frozenset to SUPPORTED_SIMPLE_VSO_ATTRS.
2. Put the raise block in proper position.
3. Changed the error message.
4. Removed test.sqlite.
Changed frozenset values to lowercase; made 'if' block check for typ.lower().
Added 'starred' to the frozenset in a bid to please Travis
Added derdon's changes.

1. Removed 'starred' from frozenset.
2. Added check for typ.lower() for 'starred'.
Fix for NotImplementedError being unnecessarily raised.

1. Put 'starred' in frozenset SUPPORTED_NONVSO_ATTRS.
2. In the typ.lower() check, used a unionized set from the vso and nonvso attrs.
Merge pull request #801 from VaticanCameos/derdonNIError

Implemented derdon's request for NotImplementedError.