Added foreman recipe as alternate local_env_file gem.

The current gem has Figaro gem support via the `:local_env_file` preference, but Figaro isn't the only gem in town that does that. I changed the config from a boolean to a multiple-choice and added support for Foreman, which is our preferred env config gem, since it also has process management capabilities using a standard Heroku- and Upstart-compatible Procfile.

For our local recipe, we also have sample Procfiles that get copied from an example repo based on which production webserver was chosen (thin, unicorn, or puma), but we can add that in later.