Fix views namespacing errors

If we try to namespace our views (e.g. posts/new.hbs), grunt will throw an error 
```bash
Cannot find module '..../app/views/posts' Use --force to continue.
```
This is happening in the browserify grunt task where the src pattern is set to '**/*'. This commit specifies the src file patterns that we're interested in, namely: .hbs and .js.