Fixing many minor issues

PTAL.

Please review using the whitespace-insensitive flag: https://github.com/es6rocks/harmonic/pull/60/files?w=1

I'll edit this description soon to add links to the bugs that are being fixed.
Avoid wrapping synchronous code in promises. https://github.com/es6rocks/harmonic/issues/53#issuecomment-59157424

Though, we could also just `Promise.resolve()` in core.js and remove `parser.start`.