Back when the Django Evolution unit tests were converted from

docstring-based tests to proper unit test suites, the signature tests

were left alone. Most of those tests weren't actually that useful

anymore, as the new tests covered the majority of what those were

testing. They also had a tendency to fail during debugging, since they

depended on printed output, and any debugging output would break all the

tests (and potentially impacting other tests as well).
This change removes the old tests, introducing newer tests for diffs and

signatures that are more comprehensive. As part of this, some

compatibility functions were introduced for checking routers, and

Unit tests pass on Django 1.6 through 1.10.