Autotest fixes

This fixes an issue with --autotest when multiple paths were given. It would register the same watcher multiple timers.  Also adds a --watch argument, to allow for watching a directory other than the specs directory.  This tidies up the autotest block in cli.js a bit, so I've removed the "TODO: is ugly - refactor" - I still wouldn't call it pretty, but it's certainly better than it was.

I'd like to add some tests for autotest.js - would there be any objection to adding [mockery](https://github.com/mfncooper/mockery) to the devDependencies to allow this?  Or rather refactor autotest.js to be more testable?