(yoyo) fixes #44 - runs generator without spawn.
Merge pull request #45 from stephenplusplus/master

Run generators in same context
Show the pretty bye message @stephenplusplus created

on forced exit too.
Removed built-in generator registration

We don't bundle generators with yo anymore.
Mock the hell out of `yo` status code test

This replaces calls to `process.exit` and `Generator.lookup` with fakes so we
can test that `yo` correctly fails when an non-existing generator name is
provided without waiting for 50+ seconds.