Update sample ruby gitlab template
Update sample ruby gitlab template

Rather than explicitly installing the capistrano gems necessary to do a
deployment, we update the sample file to:

- Assume the capistrano gems are grouped in the Gemfile as the :deploy
  group
- Use BUNDLER_WITHOUT environment variable to instruct Bundler to not
  install the :default, :development, and :test gems
- Use the BUNDLER_WITH environment variable to instruct Bundler to
  install the :deploy group
- Run bundle install to use the Gemfile instead of the explicit gem
  install commands

ucsdlib/DeveloperGuides