Basic --heroku installation support
Tweak to work in the test app
First part of refactoring CLI::Install
Finish refactoring CLI::Install to use Template Method
Rename configurator to installer
remove unneccessary attribute
Add key accessor
Move writing rails config to DefaultInstaller
Move writing standalone config to StandaloneInstaller

Don't remove code in Configuration yet as it's used by the github
installer
Make GithubInstaller a subclass of StandaloneInstaller
Move writing github config to GithubInstaller

Also stop standalone specs actually writing files
Better stub/test for standalone config being written
Use writer rather than stub
Don't use generic path when we can be specific
Encapsulate working out config_dir name
Push create_config_dir down to DefaultInstaller
Move rails config writing to own method
Write the heroku config
Actually write the API key from heroku
Don't pass the key to validate around