Changed voting dialog to only display one tab per answer.

No tests for this, yet.

Conflicts:
	common/lib/xmodule/xmodule/crowdsource_hinter.py
	common/templates/hinter_display.html
Fixed tests to work with new vote-tabbing method.  Fixed some string-int incompatibility errors.

Conflicts:
	common/lib/xmodule/xmodule/crowdsource_hinter.py
	common/lib/xmodule/xmodule/tests/test_crowdsource_hinter.py
Refactored formula response grader to expose formula-evaluating to outside world.

In preparation for adding hints to formula response.
Hinter now works with formula responses.  Tests broken.
Crowdsourced hinter now supports formula responses.  Tests still broken.
Fixed numerous 500 errors that result from mal-formatted post requests.

Fixed tests to work with symbolic answer changes.
Changed hint voting ui to show all hints on one page.

Fixed broken tests for hint manager.
Fixed monkey-patching persistent state bug.
Got rid of answer signatures - these don't work with approximate answers at all.  Instead, implemented comparison-based hint matching.

Tests are broken, hint manager is probably broken.
Fixed tests for removing hash access to hints.  Fixed instructor view for same.
Fixed a bug in recording hints shown.

Removed the answer display next to voting.  (This was deemed distracting.)
Added comments to explain confusing field names in crowdsource_hinter.

Fixed some pep8 errors.
Added tests for validate_answer in response types.
Fixed bug where user isn't asked to submit a hint unless he's seen a hint.
Addressed pull request comments.

Fixed broken tests.
Addressing more PR comments.  Fixed a test that broke when new code came in.