Add centos/redhat 7 support

The version scheme between RHEL7 and CentOS7 differ. This enburdens
us to make quarterly changes to keep this cookbook functioning if
we are explicit with versions.
By making systemd 'default' for rhel family, we can take advantage
of the regular version scheme of 6.x to correctly identify them
as 'sysv'. So, 'systemd' is now the default for this family.
Add el6.6 to attributes
Added support for the 'insecure-registry' docker daemon option.
Added support for the 'registry-mirror' docker daemon option.
Deprecate the 'restart' daemon option (obsolete since docker 1.2.0).
Added docker_container 'restart' attribute (no, on-failure, always).
Upstart: install inotify-tools only once (avoid CHEF-3694 warning).
Merge pull request #239 from jperville/chef-3694-install-inotify-tools-only-once

Upstart: install inotify-tools only once (avoid CHEF-3694 warning).
Merge pull request #237 from jperville/deprecate-daemon-restart-option

Deprecate the 'restart' daemon option (obsolete since docker 1.2.0).
Merge pull request #238 from jperville/container-restart-policy-attribute

Added docker_container 'restart' attribute (no, on-failure, always).
Merge pull request #232 from jperville/insecure-registry

Added support for the 'insecure-registry' docker daemon option.
Merge branch 'registry-mirror' of github.com:jperville/chef-docker into jperville-registry-mirror
Added support for the 'registry-mirror' docker daemon option.
Fixed dead service containers not being restarted on docker_container :run
Merge pull request #240 from jperville/container-action-run-restarts-service-when-container-down

Fixed dead service containers not being restarted on docker_container :run
Added docker_container action :create (wrapper to 'docker create').
Made container_action :redeploy use create or run depending on running?
Made docker_container action :remove remove the actual upstart service file.
Merge pull request #244 from jperville/fix-container-action-remove-with-upstart-service

Made docker_container action :remove remove the actual upstart service file
Merge pull request #242 from jperville/container-action-create

Added docker_container action :create (wrapper to 'docker create').