add travis button to README

* Add MacOS support; fix Issue #352

* On MacOS, only attempt download if condition

Add if salt_settings.install_packages to requisites for an attempt to download the minion package on MacOS

* Update example pillar for MacOS support

Describe how to use MacOS specific options

* Add MacOS notes

* Update README.rst

* Update README.rst

issue #180

This reverts commit 7bb82b0178.

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

* 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

Add modules for gitfs dependencies and documentation for how to use them.

This state downloads formulas from git repositories and ensures
that they are recorded in the file_roots setting.

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