Force Ruby version with a `.ruby-version` file
* it ensures the created project will use this version too
Configure simple_form
Create a Heroku production app too
* set `SECRET_KEY_BASE` for production too
* add git production remote
* delete unused private method
Remove handling of Ruby version patch level
* no more necessary since 2.1.0 which follows Semantic Versioning
Use PostgreSQL 9.3 on Travis CI
Heroku's default is Postgres 9.3 [1], but Travis' default is Postgres 9.1 [2]

[1]: https://devcenter.heroku.com/articles/heroku-postgresql#version-support
[2]: http://docs.travis-ci.com/user/using-postgresql/