code: function addToQueueConcat(sources, dest, options) {
        queueConcat.push({
          src:     sources,
          dest:    dest,
          options: _.extend({}, defaultOptions, options || {})
        });
      }
docs: Concat many source to dest
  
  @param {Array} sources
  Array of source path
  
  @param {String} dest
  Destination path
  
  @param {Object} options
  Transfo options object
  
  @return {Promise} TODO