Cleanup gemspec using more recent idioms.

This makes the gemspec follow idioms that are present when creating a
gem using the bundle gem command. This means we can remove the
development dependancy on jeweler.
Clean up spec_helper and make specs run in random order.
Rename license file.
Add travis.yml.
Add simplecov and coveralls.
Clean up readme.

- Move changes to a separate file
- Add badges for travis, coveralls, codeclimate and gemnasium
Remove legacy .document file.
Specify random test order in spec_helper.
Add pry for debugging.
Add thor as a dependancy.
Add a helper method for testing IO in RSpec.
Rename current spec as it only tests one class.
Refactor CLI class using thor.

- Introduce a separate Config class for inspection of the environment
- Specs are still need to be written.
Fix type in require.
Fix errors in CLI refactor. Add some complete and pending specs.
Clean up readme and add contributing guide.
Print tests in nested format.
Flesh out Config class and complete specs for Cli class.
Fix spec for checking if tmux is installed.
Rename helper module to util. Remove unneeded code from cli class.