To match the one used by the bootstrapper. Otherwhise, we end up with two repos configured

Use py3 for latest salt version
Use Python 2 on old distros
Update Gemfile
Updated centos-6 run_command, as it does not use systemd
Added tests to verify correct package versions for all cases tested

SaltStack provides "versioned" repositories, this commit add a way
to set which release of salt to use.
It adds a pillar "salt:release" which can be set to a specific release
(ex: 2016.11). This release is then used to configure properly the
repositories URLs for Debian/Ubuntu/RedHat.
The default behavior is to point to 'latest', retaining the previous
behavior if the "salt:release" pillar is not set.

Rasbian reports back the following grain values:

local:
    ----------
    os:
        Raspbian
    os_family:
        Debian
    osarch:
        armhf
    osmajorrelease:
        8
    osrelease:
        8.0

Ubuntu reports back the following grain values:

local:
    ----------
    os:
        Ubuntu
    os_family:
        Debian
    osarch:
        amd64
    osmajorrelease:
        14
    osrelease:
        14.04

For Raspbian the osarch needed to be changed from other Debain os_family
distributions.
For Ubuntu the osrelease value is needed instead of osmajorrelease as other
Debian os_family distributions.

Part of #180

Signed-off-by: Rene Jochum <rene@jochums.at>

issue #180

* Install pygit from package
* Add Official Salt ZeroMQ 4 COPR repository

Note that Salt itself is assumed to already to be available to the system via yum, via EPEL for example

fixes #83 by wrapping contents of pkgrepo/init.sls in an {% if %}.

Change-Id: I8260fdf5cf802c0b28197516da374add6c3002a2

This state enables the official saltstack package repository in order to
always benefit from the latest version. This state currently only works on
Debian and Ubuntu, and aims to implement the installation recommendations
of the official documentation:
http://docs.saltstack.com/en/latest/topics/installation/index.html