Updating the environment used by the update hook to rbenv ruby

It appears that the "update" hook from gitlab-shell defaults to
system ruby, raising errors on mismatched versions for rake when
trying to edit files using the web interface.
Forcing it to use rbenv ruby solves the issue.
Adding spec tests for update hook template
gemfile: Unpin rspec and puppet-lint gems
Convert specs to RSpec 2.99.2 syntax with Transpec
(qa) Fix lint issue due to puppet-lint 1.0.1 upgrade
Remove charlock_holmes gem resource. This is handled by GitLab itself (See Gemfile.lock)
Move dependencies class include into init.pp
Move user/home related resources to gitlab::user
Add gitlab_rails_env parameter
Make use of $gitlab_rails_env
Rename gitlab_without_gems to gitlab_unused_gems to better describe what the variable is used for.
Bump to latest stable version