non-Omnibus to Omnibus upgrade path doc

closes #97

quick guide to upgrade from non Omnibus installation to an Omnibus install

supportes both mysql and postgresql

Change ssh port

this adds a parameter to change the ssh port. useful behind firewalls.

Fix DB Port - Fixes #121

DB Port was previously defaulted to 6379 (redis port) instead of the default Postgres port 5432.

this is useful when running gitlab behind a firewall/gateway.

Gitlab yml location

Explain supervise_redis_sleep error

Update doc branch

Update runit recipe

Source:
https://github.com/opscode/omnibus-chef-server/blob/bc429109ab974f7bc5775123e8b1fe95931ce5a9/files/chef-server-cookbooks/runit/recipes/default.rb

Source sauce

This will quiet warnings at the start of each `gitlab-ctl reconfigure`
run.

Platform Directory

Source:
https://github.com/opscode/omnibus-software/blob/a08918d84cb4ae31d4c749167def662350aa6235/config/software/cacerts.rb

Select Documentation Version

Update Build Documentation

Explain Underscores