Restore unit tests in classes starting with Test

https://github.com/sqlalchemy/mako/commit/7e52b60b7dac75a3c7177e69244123c0dad9e9d9 changed tests from `unittest.TestCase` to pytest collection.  But since then only classes *ending* in the word `Test` were considered to be tests; classes *starting* in `Test` were not.  This disabled some existing tests, and while renaming these would be a viable way to restore coverage, extending the list of test class names avoids accidentally missing similar classes in the future.

The loop test classes make use of the `setUp` method, so in their current form they need to inherit from `unittest` again.  Changing to pytest fixtures would be a possible future modification.

This commit adds 33 tests that had been missing before:
* 25 methods in 4 classes from `test_loop.py`
* 2 methods in `TestTemplateAPI` from `test_template.py`
* 6 methods in `TestTGPlugin` from `test_tgplugin.py`

Closes: #365
Pull-request: https://github.com/sqlalchemy/mako/pull/365
Pull-request-sha: 6b5ff13dd5346f3472ac93f3af0a9da172ae1c5e

Change-Id: I744b8c6f28cf485c07cd30a11c328ea7391c7d3b
2 files changed