* Modifies systemd? behavior.

- Checks for the presence and executable-ness of 'systemctl', similar to the pattern used for other supervisors.
- This also help support cases where chef-sugar is used on containers (i.e. for unit testing) where /proc/1/comm will not be 'systemd' but the name of the process running in the container (i.e. 'bash' or 'ssh').

Signed-off-by: Ryan Frantz <ryanleefrantz@gmail.com>

* Bumps version and upadtes CHANGELOG

Signed-off-by: Ryan Frantz <ryanleefrantz@gmail.com>

* Update to use File::exist?

- This should properly cover all Linux distros like RHEL, Ubuntu, and SLES because they have, at a minimum, a symlink at /bin/systemctl.
- NOTE: All distros except Ubuntu have /usr/bin/systemctl. Weird, eh?