Checkstyle updates for Unit Tests

Handles https://github.com/Jasig/cas/issues/757

So I realized our checkstyle is not actually covering tests. So I made the change to do so and in the process applied a few fixes as well. This is a really boring pull as it entirely should just affect unit tests. This is what has happened:

1. Disallow the use of `testMethod` for JUnit tests. As @battags brought this up, using a `test` prefix is unneeded with annotations.
2. All tests should now have proper javadocs for author and since tags. 
3. We are ignoring the MagicNumber check for tests. Everything else still applies, and I managed to fix parameter ordering, variable naming styles, etc all in tests, which should all pass :)
Amounts to the same thing really, force of habit.