code: function _getSource() {
  		var application = 'axeAPI',
  			version = '',
  			src;
  		if (typeof axe !== 'undefined' && axe._audit && axe._audit.application) {
  			application = axe._audit.application;
  		}
  		if (typeof axe !== 'undefined') {
  			version = axe.version;
  		}
  		src = application + '.' + version;
  		return src;
  	}
docs: get the unique string to be used to identify our instance of axe
  @private