v0.4.0 - implement testF() and testingF() macros

• 0.4.0 (2018-03-30)
  • Implement testF() and testingF() macros for using test fixtures.
  • Added examples/fixture/ sample code.
  • Removed support for manual Test and TestOnce test instances. Use
    testF() and testingF() macros instead.
  • Renamed Test and TestOnce class hierarchy into TestAgain and
    TestOnce respectively, and made them siblings not parent/child.
  • Implement early return upon delayed failure (assertions check the test
    status and return early).
  • Add ability to control verbosity on a per-test basis.

Fixes #9.