Update GitLab version to 7.3.1

Update URL in template header.
Better error handling when checking for GitLab rpm

Describe how run update using tags in README.
Combine two tasks for shutting down services using with_items.
Instead of starting unicorn and sidekiq, restart all GitLab services.
Only enable SSL if private and public key vars are defined
Fix spelling error in comment
Improve update playbook

Move conditonal include of update playbook further up in the main playbook. This makes later tasks, like modifying the git user account, make more sense because they don't exist until GitLab is installed.

Add "UPDATE | " to all tasks in the update playbook so they are easy to distinguish when running.

Change GitLab reconfigure and restart tasks in the update playbook to handlers. This prevents multiple executions of gitlab-ctl reconfigure if the gitlab.rb file is updated at the same time GitLab is updated (or installed initially).

Add handler to wait for unicorn to come back up.
Merge branch 'feature/better-ssl' into develop
Update GitLab version to 7.3.2
Bump version number to 1.1
Merge branch 'release/1.1'