Add upgrade button. #51

Author: timwis

admin.html

@@ -49,6 +49,12 @@ <h3>Authentication</h3>
 
     <button type="submit" class="btn btn-primary">Submit</button>
 
+    <h3>Site Maintenance</h3>
+
+    <div class="form-group">
+      <a href="https://github.com/{{ site.github.owner_name }}/{{ site.github.project_title }}/compare/gh-pages...timwis:gh-pages?expand=1" class="btn btn-info">Check for updates</a>
+    </div>
+
   </fieldset>
 
 </form>