Rename helper module to util. Remove unneeded code from cli class.
Add activesupport gem.
Remove Gemfile.lock.
Add a project class to represent a tmuxinator project.
Major refactor of tmuxinator config representation.

- Test coverage is > 90% :sparkles:
- Create a pane class to represent a single pane
- Create a tab class to represent a single tab, with a list of pane objects
- Flesh out the project class, now containing a list of tab objects
- Remove the config writer class
- RVM/rbenv support broken with this refactor