Create a system usergroup if user is a system user

If the user to be created is a system user, it makes no sense to create
him a primary group which is not a system group too.

Resolve `git.config` error where minion does not have Git installed #115

Default path for home folder in user_files.sls if home omitted in pillar [fixed style].

Pull changes from master

Pull changes from main repo.

Revert "User files state without defined home directory"

User files state without defined home directory

also load ssh keys from pillar data

Pull changes from main repo.

Pull changes from main repo.

Use the primary group for the user when creating authorized_keys

If a primary group is set on the user, and a authorized_keys is provied in ssh_auth_file, the formula fails. This solves that by using the user_group set earlier in the formula

Mitigate Salt issue #29004, fixes "expire" on *BSD

Unreasonable values for 'expire' (after 9999-12-31
on Linux, before 1975-01-01 on *BSD) get divided
by 86400 (number of seconds in a day) when too big
or multiplied by 86400 when too small.

Tested on CentOS 6 (Salt 2015.5.5) and FreeBSD 10.2
(Salt 2015.8.0) with following values:

  - 24854 (2038-01-18 in days since epoch)
  - 157766400 (1975-01-01 00:00:00 UTC in seconds since epoch)
  - 3313526400 (2075-01-01 00:00:00 UTC in seconds since epoch)
  - 16000 (2013-10-22 in days since epoch)
  - 18000 (2019-04-14 in days since epoch)

(Sponsored by av.tu-berlin.de and fokus.fraunhofer.de)

Don't add sudo group by default.

Pull changes from main repo.

Default path for home folder in user_files.sls if home omitted in pillar.

update pillar.example to include uid

in an attempt to save others from digging into the source (to confirm this detail)

Fix for:
Rendering SLS 'base:users.user_files' failed: Jinja variable 'dict object' has no attribute 'home'

Adds 'empty_password' statement for states.user.present (issue #97)

changing visudo checking to avoid wrong reporting when launched in a test mode

Fix minor bug for ssh known_hosts management with salt >= 2015.5.5.

This version complains that "argument port can not be used in
conjunction with argument hash_hostname", so add hash_hostname
to the fields we handle in the formula so we can override it
if needed.

Added ability to specify room number, home phone, and work phone

Add possibility to manage the user's global git configuration.

Add possibility to manage ssh's known_hosts file.

Manage arbitrary user files

Add ssh_auth_pillar option.