Hide menu and show it when hitting button.

Closes https://gitlab.com/autonomic-cooperative/autonomic-cooperative.gitlab.io/issues/28.

src/assets/styles/components/_menu.scss

@@ -21,6 +21,7 @@
 }
 
 #menu {
+  display:none;
   @include vendor('transform', 'translateX(20em)');
   @include vendor('transition', 'transform #{_duration(menu)} ease');
   -webkit-overflow-scrolling: touch;