cookbook versioning

Cookbook Versioning and Tracking

@temujin9 please complete and correct

• git tag labels the release of a cookbook version: tag 'cookbooks-elasticsearch-3.1.7' denotes the last commit to that tag.
• The next commit will be the one that bumps the version number: the metadata.rb will then read '3.1.8'.

Periodically, we will release a 'gold' version set and push those to the opscode cookbook community site.