Added reference to the line "ENV['RAILS_RELATIVE_URL_ROOT'] = "/gitlab"" , as it talked about in the gitlab.yml.example

This commit addresses two related issues:
- Sidekiq should shut down completely before we restart it;
- If we restart unicorn with USR2 we need to kill the old master and
  worker processes.

otherwise it will listen on 0.0.0.0

Most of these are comments but a few are strings for users.

Might be an idea to run this from time to time:
https://github.com/lyda/misspell-check

It runs mostly clean now.

The timeout was changed to 30 and the comment wasn't updated. Also I've seen several reports of this timeout not being long enough for quite a few people. It resulted in me getting a 502 bad gateway from nginx until I upped it. Perhaps could back to the default 60 would be better? I changed mine to 300, running on an AWS micro instance.

Renamed unicorn.rb.orig to unicorn.rb.example since this seems to be more in line with the common used naming in the config directory. Plus seeing *.orig files I think of the leftovers of git merges, which left me puzzled for quite some time.