prompt to create a new .html.erb file if controller view wasn't found

Also removed some whitespaces :(, my atom config does this automatically. I'm sorry if is an issue.
I think that JSON schema configuration is better than configDefaults object.
http://blog.atom.io/2014/10/02/config-api-has-schema.html
https://atom.io/docs/api/v0.152.0/Config
https://github.com/atom/atom/blob/master/src/config-schema.coffee

e.g.
```
module.exports = 
  config:
    newFileExtension:
      type: 'string'
      default: 'html.erb'
```