update elements and fix some bugs

lib/src/paper-tooltip/test/test-button.html

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 <link rel="import" href="../../polymer/polymer.html">
 <link rel="import" href="../paper-tooltip.html">
 
 <dom-module id="test-button">
   <template>
     <style>
       :host {
         display: inline-block;
       }
 
       #button {
         width: 100px;
         height: 20px;
         background-color: red;
       }
+
       paper-tooltip {
         width: 70px;
+        height: 30px;
       }
 
     </style>
 
     <div id="button"></div>
-    <paper-tooltip id="tooltip" for="button">Tooltip text</paper-tooltip>
+    <paper-tooltip id="buttonTooltip" for="button">Tooltip text</paper-tooltip>
   </template>
 
   <script>
     Polymer({
       is: 'test-button'
     });
   </script>
 </dom-module>