Building an image requires systemd to be installed in the rootfs as the
init daemon, so assert that systemd is available.
Updated tests so that alpine is only tested as an initrd (it cannot be
an image as it doesn't use systemd).
Added warning note about alpine to the docs.
Fixes#98.
Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>
Rework the docs to make them simpler and more consistent. Also added of
contents and corrected a few mistakes.
Fixes#26.
Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>
