Adding post-card.html to avoid 404s in first step solution.

samples/tutorial/step-1/post-card.html

@@ -0,0 +1,28 @@
+<link rel="import" href="../components/polymer/polymer.html">
+<link rel="import" href="../components/core-icon-button/core-icon-button.html">
+
+<polymer-element name="post-card">
+  <template>
+    <style>
+    :host {
+      display: block;
+      position: relative;
+      background-color: white;
+      padding: 20px;
+      width: 100%;
+      font-size: 1.2rem;
+      font-weight: 300;
+    }
+    .card-header {
+      margin-bottom: 10px;
+    }
+
+    </style>
+
+    <!-- CARD CONTENTS GO HERE -->
+
+  </template>
+  <script>
+  Polymer({});
+  </script>
+</polymer-element>