message: add filter method
diff: @@ -13,6 +13,13 @@ export default class FieldBag {
  return find(this.items, item => item.matches(matcher));
  }
  + /**
  + * @param {Object} matcher
  + */
  + filter (matcher) {
  + return this.items.filter(item => item.matches(matcher));
  + }
  +
  /**
  * Finds and removes the first field that matches the provided matcher object.
  * @param {Object} matcher
  @@ -26,5 +33,8 @@ export default class FieldBag {
  this.items.splice(index, 1);
  }
  -}
  + push (item) {
  + this.items.push(item);
  + }
  +}
  