feat(viewport): add viewport meta tag for mobile screens

Author: jeffbcross

addon/ng2/blueprints/ng2/files/__path__/index.html

@@ -7,6 +7,7 @@
   {{content-for 'head'}}
   <link rel="icon" type="image/x-icon" href="favicon.ico"><% if (isMobile) { %>
   <link rel="manifest" href="/manifest.webapp"><% } %>
+  <meta name="viewport" content="width=device-width, initial-scale=1">
 
   <!-- Service worker support is disabled by default.
        Install the worker script and uncomment to enable.