Add the rails_helper when creating a new app

Closes #348 

Guys, plz review with care. I move things from one place to another, more info on the commit message. The important here is to check if dont remove anything by mistake.
Take a look [here](https://gist.github.com/TiuTalk/551378d3451361be0212#file-spec_helper-rb-L52-L56)