Add `change-extension` script

Add ability to change file extensions of files recursively in current
directory.
Add submodules to repository.
Change vim colour scheme to Tomorrow Night.
Add user details to Git config.
Make it easier to navigate between Vim splits.
Update the rspec alias to bundle exec.
Remove rake zsh function.
Add Vim Powerline.
Add Solarized Powerline theme and colours.
Add Solarized colours.
Setup Solarized colours.
Remove Tomorrow Night colours.
Remove unwanted bundles.
Untrack submodules.
Bundle Solarized colours.
Add Heroku to the path.
Setup Vim to switch between specs.
Add an alias for MyOTB.
Add an alias for the dotfiles project.
Add an alias for the OTB Geolocation app.