Allow CHEF_VERSION to include requirement specification
Allow CHEF_VERSION to include requirement specification

For example '~> 10' and '~> 0.10.6' can be used.
'10.18.2' still uses the specific version.

reaktor/chef-debian,bitmonk/chef-debian,reaktor/chef-debian,bitmonk/chef-debian,reaktor/chef-debian,bitmonk/chef-debian