Debian packaging with pkgr

Created by: crohr

Hi,

This pull request is a work in progress to make Gitlab easily packageable with pkgr. Basically I'm trying to make the main configuration available through environment variables, and making the necessary changes so that it can be run through the Rails heroku buildpack without error.

You can see a result of this work at http://deb.pkgr.io/crohr/gitlabhq/, where I've managed to automate the making of a debian package based off the master branch.