test cases for SurveryResponseForm
Squashed commits:
[58b4f8e] Better error messages to be in line with standard error messages
[625f12d] Explicit import of auth User as it was causing issues in the Form tests
[f45088e] Adding test cases for SurveryResponseForm
Moving result from function based view to class based view.

Adding new mix in for authorisation checks.  This is to allow a more flexible approach to authorisation in the future.

Also update template to use context object for data.  UX improvement to warn user if no result have yet been recorded against a temp.

Adding coveralls for a published view of code coverage pushed out form build.

Adding coverall coverage badge for quick coverage and link to metrics on coverall.
Adding tests for submit function based views.

Requires addition of mock library to remove difficulty of manipulating sessions in django test client.  This allows me to mimic the behaviour of a user session in the submit view for an existing survey response.

Have added tests around form validation rules.