Fix closing tag in example page

Author: muan

examples/index.html

@@ -13,7 +13,7 @@
         <md-quote class="btn btn-sm">quote</md-quote>
         <md-code class="btn btn-sm">code</md-code>
         <md-link class="btn btn-sm">link</md-link>
-        <md-image class="btn btn-sm">image</md-link>
+        <md-image class="btn btn-sm">image</md-image>
         <md-unordered-list class="btn btn-sm">unordered-list</md-unordered-list>
         <md-ordered-list class="btn btn-sm">ordered-list</md-ordered-list>
         <md-task-list class="btn btn-sm">task-list</md-task-list>