Fix broken tests

Updates to Mocha and CoffeeScript broke our tests. The problems were easily fixed, but we may want to consider locking down the version numbers. 

## Mocha 1.9
`--ignore-leaks` was replaced with `--check-leaks`. Leaks are now ignored by default, so removing the offending line fixed the problem.

> By default Mocha will not check for global variables leaked while running tests, to enable this pass use `--check-leaks`

## CoffeeScript 1.7 
Mocha broke with the introduction of CoffeeScript 1.7. See [this issue](https://github.com/visionmedia/mocha/issues/1120) for more details.