Upgraded ubuntu image to 14_04.
Added variables for postgres, ruby and ruby-install.
Used the postgres version variable during postgres installation.
Better indentation into the git task file.
Ruby-install uses the playbook variable (also a small refactoring provided).
Git external ppa enabled.
Skip ruby installation if already installed.
Improved readability of the zsh task file.
Skip zsh task if .zshrc exists.
Better syntax for the chruby file and chruby version variable.
Ruby version variable for bundler installation.
Bundler installation does not require ruby hardcoded version.