Fix some issues + last stand

Signed-off-by: Josef Fröhle <github@josef-froehle.de>

assets/js/hamburger.js

@@ -0,0 +1,7 @@
+function toggleHamburger () {
+  $('.hamburger').toggleClass('is-active');
+}
+
+$('.hamburger-button').on('click', function () {
+  toggleHamburger();
+});