Managing postfix conflict

This wouldn't seem necessary because of the use of ensure_packages, but
unfortunately it's not a perfect function and only works if everyone
uses it. The thias/postfix module declares the Postfix package with
different parameters, and should probably take priority for the
package. This simple flag disables this module's (already really light)
management of the Postfix package if need-be.
My bad, forgotten change fixed
Wow I am not with it today; fixed other thing
Merge pull request #145 from andschwa/postfix

Managing postfix conflict
Update readme/changelog (gitlab_ensure_postfix)
Removing backup script and cron job when false

In case someone (like me) had previously enabled the backup and wants to
disable it, doing so with Puppet is easy enough.
Merge pull request #147 from andschwa/backup-absent

Removing backup script and cron job when false
Remove reaping frequency

Upgrade step 5 suggests removing ```reaping_frequency``` to prevent crashes.
Also fixes #142.
Disable gzip compression if SSL enabled

Per the upgrade documentation, gzip compression should be disabled if SSL is in
use to prevent BREACH attacks.
Enable gzip compression for static assets

Upgrade documetnation recommends this based on Rails notes for the asset
pipeline.
Update gitlab.yml template
Version update
Merge pull request #149 from atomaka/atomaka/feature/6.8

GitLab 6.8
Allow adjustment of number of bundler threads
Merge pull request #150 from atomaka/atomaka/feature/multi-bundle

Allow adjustment of number of bundler threads
simplify backup ensure => absent, as per my own comments
Merge pull request #152 from igalic/simple-absent-backup

simplify backup ensure => absent, as per my own comments
Bump branch tags for gitlab and gitlab-shell
Update gitlab.yml config file

There are several new settings we may consider adding.

* ssh_host
* signin_enabled
* repository_downloads_path
The gitlab-satellites permissions should be 0750

Otherwise the built-in GitLab environment check gives a warning and says to fix it; these are the fixed permissions.

The [installation documentation](https://github.com/gitlabhq/gitlabhq/blob/master/doc/install/installation.md#configure-it) says `sudo chmod u+rwx,g+rx,o-rwx /home/git/gitlab-satellites` which translates to 0750 permissions.