Add factoryboy Project and Allocation unit tests

[claire-peters]

This PR includes:

• building out of the test_helpers/factory.py module, particularly Project and Allocation-related factories.
• unit test utility functions
• unit tests for Project models and views
• unit tests for Allocation models and views

There are also a couple of minor changes made to the Allocation views:

• remove login_url from AllocationChangeListView so the redirect when not logged in will be to '/user/login?next={page}'
• add success message to AllocationCreateView post request (successful submission of an allocation creation request now includes a corresponding success message)

Looking forward to your comments!

[claire-peters]

Thanks for catching the issues there - the parts for #541 should be in a separate PR, and I'm happy to put off any formatting changes to the user tests module until it can be paired with a more substantive contribution to said module. Just pushed my changes, let me know what you think.

[claire-peters]

Whup, thanks for catching that. Added the changes to make the tests work - specifically, I made it so a success message would appear on the following page after an allocation request has been successfully submitted and I removed the line login_url = '/' from AllocationChangeListView. If there are any issues with this, just let me know.