BREAKING CHANGE closes #873 - errors inside observers are not caught

I'm a big TJ Holowaychuk fanboy, so you don't have to sell me on mocha. But honestly qunit hasn't been so bad once we got the auto-create runner.html worked out. Of course, we wouldn't need nodeunit with mocha for .toHTML tests...

Phantom on the other hand... Do we know JSDOM would be any better?