Make SkyElement more classy.

sky/examples/file-browser.sky

Index: sky/examples/file-browser.sky
diff --git a/sky/examples/file-browser.sky b/sky/examples/file-browser.sky
index ba456ae9e3f1d1bda820aa63d46c8b00d2dfb642..f71672c36d6b4c96c05515fe8e59f5315c023024 100644
--- a/sky/examples/file-browser.sky
+++ b/sky/examples/file-browser.sky
@@ -6,6 +6,7 @@
 <import src="../framework/sky-element/sky-element.sky" as="SkyElement" />
 <import src="../framework/xmlhttprequest.sky" as="XMLHttpRequest" />
 
+<sky-element name="file-browser">
 <template>
   <style>
     heading {
@@ -21,12 +22,13 @@
   </template>
 </template>
 <script>
-SkyElement({
-  name: 'file-browser',
-  url: '',
-  files: [],
-  directories: [],
-  attached: function() {
+module.exports = class extends SkyElement {
+  created() {
+    this.url = '';
+    this.files = [];
+    this.directories = [];
+  }
+  attached() {
     this.url = this.ownerDocument.URL;
     var xhr = new XMLHttpRequest();
     xhr.open('GET', this.url + '?format=json');
@@ -37,5 +39,6 @@ SkyElement({
     }).bind(this);
     xhr.send();
   }
-});
+}.register();
 </script>
+</sky-element>