Hide welcome page sidebar on mobile

Use Lato as font for welcome page to make it visually consistant with our
website.

h/static/styles/help-page.scss

@@ -4,6 +4,7 @@
   padding-top: 2.5em;
   padding-bottom: 2.5em;
   background: $body-background;
+  font-family: 'Lato', sans-serif !important;
 
   @include breakpoint(920px) {
     padding-right: 460px;
@@ -156,3 +157,13 @@
     font-size: 12px;
   }
 }
+
+/*
+  Mobile layout
+*/
+
+@media screen and (max-width: 30em) {
+  .help-page-sidebar {
+    display: none;
+  }
+}