Thor init

@jrpatterson I started a new branch for our work session tomorrow afternoon. So far I have the following set up:

- Thor is loaded
- There's a `GPGroup` class that's hooked up to Thor
- There's an empty `gpgroup init` command, which I figure will be the simplest thing for us to implement first
- There's a `gpgroup` executable that's hooked up to the `GPGroup` class
- There are test-driven specs for all of the above
- The gemspec is set up to package and distribute things properly

…but there isn't a single bit of "real" application code yet.

This should give us some good infrastructure and a good initial starting point. I think the next step can be to roll up our sleeves and use this to implement the first command. 

If you want to check out what I've done so far:

1. Go to your copy of the source
1. Fetch my changes: `git fetch`
1. Check out this branch: `git checkout thor-init`
1. Make sure you have the right gems installed: `bundle install`
1. Run the tests: `rspec`

Let me know if you have any trouble!