code: function targz(stream, opts) {
    return exports.tar(stream.pipe(zlib.createGunzip()), opts);
  }
docs: Gunzips the .tar.gz stream and passes it along to `tar`.
  
  @name targz
  @function
  @param {ReadableStream} stream .tar.gz stream
  @param {Object} opts @see `tar`
  @return {ReadableStream} the transformed tar stream