Roll Polymer to 1.3.1

third_party/polymer/v1_0/components-chromium/iron-test-helpers/README.md

+[![Build status](https://travis-ci.org/PolymerElements/iron-test-helpers.svg?branch=master)](https://travis-ci.org/PolymerElements/iron-test-helpers)
+
 # iron-test-helpers
 
-Utility classes to make testing easier.
+A set of utility classes to make testing easier. For more details on the methods
+available, please check the documentation of `mock-interactions.js` and
+`test-helpers.js`
 
 ## Mock Interactions
 
 This is a set of methods to simulate mouse or keyboard interaction with an element. Include `mock-interactions.js` and then use them like so:
 
 ```javascript
 test('can be triggered with space', function(done) {
   button.addEventListener('keydown', function() {
     done();
   });
   MockInteractions.pressSpace(button);
 });
 
 test('can be clicked', function(done) {
   button.addEventListener('click', function() {
     done();
   });
   MockInteractions.tap(button);
 });
 ```