API and dependencies cleanup

Remove mocha and promises from the public API, as discussed in #1.

- Add `configure` and `run` functions to execute the validation suite.

- Add `defineSuite` function that can be used to include the validation
suite in an existing Mocha test suite.

The commit making package names globally unique is not related to the API changes, it just makes it easy to run the suite repeatedly from CLI.

/to @rmg