Add RPC release identifier

Add version recipe which drops the converged release number into
/etc/rcb-release. Will include this recipe in the base role.

Fixes rcbops/chef-cookbooks#772
Merge pull request #158 from claco/issue-772

Merged automatically by jenkins after successful build test
upgrade python-six on centos
Merge pull request #159 from rackerjoe/Issue815

Merged automatically by jenkins after successful build test
added nf_conntrack_max to base
added nf_conntrack_max to base
Merge pull request #161 from cloudnull/Issue817

Merged automatically by jenkins after successful build test