Added deviance testing for submit entry form

The deviance tests fill out the form with mostly conforming data, however one piece of data is taken from the set of deviating data. The test expects the form to reject each piece of data, and fails if the form accepts a set of the data. This test is run against each deviating data item from test_data.FIELDS.

So far we're failing by accepting input from an incorrect youtube video url. However, the test seems somewhat random in its application order (it's iterating through a set), so you may find something else that fails before you test youtube urls.

Tests ran at ~60 seconds on my machine from a clean database.