Require Chef 12.15+
Require Chef 12.15+

This gives us modern metadata processing

Signed-off-by: Tim Smith <764ef62106582a09ed09dfa0b6bff7c05fd7d1e4@chef.io>

chef-brigade/etcd-cookbook,chef-brigade/etcd-cookbook,spheromak/etcd-cookbook,chef-cookbooks/etcd,someara/etcd-cookbook,chef-brigade/etcd-cookbook,chef-cookbooks/etcd,someara/etcd-cookbook,chef-cookbooks/etcd,spheromak/etcd-cookbook,spheromak/etcd-cookbook,someara/etcd-cookbook