docs: function streamFile(namespace, fileName) {
    return gfsPromise.then(function(gfs) {
      var deferred = q.defer();
      var options = {
        filename: fileName
      };
      if (namespace) {
        options.root = namespace;
      }
      var readstream = gfs.createReadStream(options);
      readstream.on('error', function(err) {
        console.log('An error occurred when reading file from gridfs!', err);
      });
      deferred.resolve(readstream);
      return deferred.promise;
    });
  }