PARSER
 Process a tag attribute
function(match, strUntilValue, name, value, index) {
  var self = this;
  var containsTemplate = false;

  // Check if attribute is included in the "attributes" option
  if (!this.isRelevantTagAttr(this.currentTag, name)) {
    return;
  }

  this.matches.push({
    start: index + strUntilValue.length,
    length: value.length,
    value: value,
    containsTemplate: isTemplate(value)
  });
}