Stop using the Whiskey shim and write using `describe` and `it`.

Closes #61.
Merge pull request #79 from eventualbuddha/move-tests-to-mocha-for-real

Stop using the Whiskey shim and write using `describe` and `it`.
Ensure printing try/catch generically works correctly.

Previously the `print` function was being called with `handler`, which was just a Node and not a NodePath, therefore the assertion in `print` was failing. This was only triggered when printing generically or printing a generated TryStatement.