Initial Gemfile, pre-bundle.

* Initial repository via. GitHub.com
* Wrote basic Gemfile, with gemset directive
* `cd`ed back into the greenthumbs directory, so that rvm would pick up on the new gemset directive

Learned that:
* `rvm list` shows available rubies and the current ruby
* `rvm gemset list` shows gemsets in this ruby, and the current gemset
* `rvm gemset delete <name>` deletes a gemset