Fix use of Mocha as test framework around ngMock

Issue #1467 describes a real problem when trying to use the Mocha support that was introduced in 1.1.1 as pull request #1253. It seems the code actually merged for #1253 differed from the original author's proposal in one key regard.

This pull request fixes #1467, and, I believe, that's also the reason for issue #1589 and why #1253 kept attracting comments after it was closed.

While I was there, I fixed a couple comments.