audit license headers

elements/css/pi-explore.css

@@ -1,3 +1,13 @@
+/*
+ * @license
+ * Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
+ * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+ * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+ * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+ * Code distributed by Google as part of the polymer project is also
+ * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+ */
+
 #viewer {
   position: relative;  
 }

elements/css/pi-home.css

@@ -1,3 +1,13 @@
+/*
+ * @license
+ * Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
+ * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+ * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+ * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+ * Code distributed by Google as part of the polymer project is also
+ * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+ */
+
 :host {
   display: block;
   overflow: auto;

metadata.html

@@ -1,3 +1,12 @@
+<!--
+    @license
+    Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
+    This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+    The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+    The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+    Code distributed by Google as part of the polymer project is also
+    subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+-->
 <x-meta id="pi-feed-viewer" label="Feed Viewer">
   <template>
     <pi-feed-viewer panel="topics" layout="quilt" topicsLayout="grid" style="width: 400px; height: 400px;"