Move away from most fixtures for the webapi tests.
This removes the usage of the test_reviewrequests and most of the

test_scmtools fixtures from the webapi unit tests. Instead, these test

suites now use the new TestCase class's utility methods for creating

test objects.
It also removes a lot of the older utility methods for creating dummy

objects that went through the API. Each of these requests contributed

50-100ms of time, which added up.
With the test suite as it originally was, on my machine, it took roughly

159 seconds to complete. After this and the previous changes, it drops

to around ~88.
Unit tests are much clearer now. Instead of having to know how fixtures

are set up, or tracing through a bunch of API requests, you can just

read the unit tests and see what they're doing.
In total, 1,823 lines of code have been deleted in these changes.

Unit tests pass.
Compared speeds and saw that tests are down to around 88 lines.
Ran pyflakes.