Merge pull request #320 from herby/async-test-refactor-readable

`RunningTestContext >> execute:` refactored for readability.
Merge pull request #321 from herby/async-test-refactor-readable

*TestContext classes refactored.
More class SUnit comments and refactorings
More SUnit tests
More small SUnit refactorings
- More Sunit refactorings and reformattings
- renamed TestCase >> graceTime: to #timeout:
Oops. Broke some tests.