Update bower.json for Polymer elements and add PRESUBMIT.py

third_party/polymer/v1_0/components/iron-collapse/README.md

 # iron-collapse
 
 `iron-collapse` creates a collapsible block of content.  By default, the content
 will be collapsed.  Use `opened` or `toggle()` to show/hide the content.
 
 ```html
-<button on-click="{{toggle}}">toggle collapse</button>
+<button on-click="toggle">toggle collapse</button>
 
 <iron-collapse id="collapse">
   <div>Content goes here...</div>
 </iron-collapse>
 ```
 
 ```javascript
 toggle: function() {
   this.$.collapse.toggle();
 }
@@ skipping 10 matching lines @@
     border: 1px solid #dedede;
   }
 </style>
 
 <iron-collapse>
   <div class="collapse-content">
     <div>Content goes here...</div>
   </div>
 </iron-collapse>
 ```