WIP: Tmuxinator 0.6.0

This pull request will contain the development for version 0.6.0 of tmuxinator. My goal is to clean up the code, increase test coverage and fix outstanding bugs for this version. Additional features can then be attempted for 0.7.0.

- [x] Clean up gemspec
- [x] Update dependancies
- [x] Add simplecov for test coverage
- [x] Setup travis, coveralls, gemnasium and codeclimate
- [x] Write specs for each of the classes, attempting to get coverage >= 80%
- [x] Clean up command completion code, taking a similar approach to how [rbenv does it](https://github.com/sstephenson/rbenv/tree/master/completions)
- [x] Refactor `cli.rb` using [thor](https://github.com/wycats/thor)
- [x] Create a `Tmuxinator::Project` class to encapsulate a single project
- [x] Fix outstanding bugs ~~#72~~ ~~#89~~ ~~#90~~ ~~#93~~ ~~#101~~ ~~#102~~ ~~#103~~ ~~#104~~ ~~#109~~
- [x] Deal with base-index once and for all
- [x] Handle `cli_args` properly
- [x] Need to add deprecations for rbenv/rvm, handling them gracefully
- [x] Update the README
- [x] Moar tests :sparkles: