Factor sky-toolbar into a componet and use a proper material shadow

sky/examples/stocks/stock.sky

 <!--
 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 -->
 <import src="/sky/framework/sky-element.sky" />
 
 <sky-element>
 <template>
   <style>
   :host {
     // TODO(eseidel): Why does setting height here make this too big?
     // height: 48px;
     max-height: 48px;
     display: flex;
-    border-bottom: 1px solid black;
+    border-bottom: 1px solid #F4F4F4;
     padding-top: 16px;
     padding-left: 16px;
     padding-right: 16px;
     padding-bottom: 20px;
   }
   #ticker {
     flex-grow: 1;
   }
   #last-sale {
     padding-right: 20px;
@@ skipping 67 matching lines @@
     if (model.percentChange > 0)
       changeString = "+" + changeString;
     change.textContent = changeString;
     change.style['background-color'] = colorForPercentChange(model.percentChange);
   }
 }
 
 _init(script) => register(script, Stock);
 </script>
 </sky-element>