Greatly improve `berks package` command

* The package command will first vendor the contents of a Berksfile
  into a temporary location before creating the archive.
* The first argument to package has been changed to be the destination
  of where to write the archive.
* Package now respects the --only and --except flag. This will ensure
  that only cookbooks found within a desired set of groups is packaged
* The destination that the outfile will be written to is now verified
  to be a valid writable directory by the process executor