Use SemVer build version for ChefDK projects

This format produced a fully SemVer-compliant build version like:

MAJOR.MINOR.PATCH-PRERELEASE+TIMESTAMP.git.COMMITS_SINCE.GIT_SHA

The timestamp can optionally be omitted by passing the `--no-timestamp` 
to the `omnibus` CLI.
Merge pull request #123 from opscode/schisamo/chefdk-semver-version

Use SemVer build version for ChefDK projects