Downgrade handlebars gem version.

If you try to install handlebars 0.4.0:

![you're gonna have a bad time](http://cdn.memegenerator.net/instances/400x/36715573.jpg)

Errors get thrown with installing libv8 if you're using XCode's gcc (which is 4.2, v8 won't deal with anything < 4.6). Downgrading to 0.3.2 seems to fix it.