update version number

smash/web/templates/_base.html

@@ -265,7 +265,7 @@ desired effect
         {% block footer %}
             <!-- To the right -->
             <div class="pull-right hidden-xs">
-                Version: <strong>preview 0.5.0</strong> (12 Apr 2017)
+                Version: <strong>preview 0.5.1</strong> (21 Apr 2017)
             </div>
 
             <!-- Default to the left -->