docs: function streamFactory( options ) {
  	var opts;
  	if ( arguments.length ) {
  		opts = copy( options );
  	} else {
  		opts = {};
  	}
  	/**
  	* FUNCTION: createStream( fcn )
  	*	Creates a stream.
  	*
  	* @param {Function} fcn - map function
  	* @returns {Stream} Transform stream
  	*/
  	return function createStream( fcn ) {
  		if ( !arguments.length ) {
  			throw new Error( 'insufficient input arguments. Must provide a map function.' );
  		}
  		return new Stream( opts, fcn );
  	};
  }