JUnit 5 support (extension instead of EasyMockRunner)

[tobymurray]

As commented here, the JUnit 4 practice of @RunWith(EasyMockRunner.class) no longer works. RunWith has been superseded by @ExtendWith.

I haven't really looked at what that implies, is JUnit 5 compatibility for the same features on the roadmap?

A StackOverflow answer has a workaround here: https://stackoverflow.com/a/47243856/2152081 - is that viable as is?

[tobymurray]

I took the code from that StackOverflow answer and used it as described, it seems to work. I can submit a PR with that class if it'd be accepted?

[henri-tremblay]

Please do. Worst case is that I'll tweak it a little

[henri-tremblay]

Close by #246