Decouple help page styles from app styles

This change introduces a new top-level stylesheet for the help page.
This will hopefully make it easier to tell where styles affecting the
help page come from, and minimise the number of times that changes to
unrelated CSS will alter the display of the help page.

h/static/styles/common.scss

@@ -18,7 +18,6 @@ $headings-color: $text-color;
 @import 'tags-input';
 @import 'topbar';
 @import 'page';
-@import 'help-page';
 
 //ELEMENT STYLES////////////////////////////////
 a {

h/static/styles/help-page.scss

+@import 'compass';
+
+@import 'reset';
+@import 'common';
 @import "./mixins/icons";
 
+body {
+  background: #fff;
+}
+
 .help-page {
   padding-top: 2.5em;
   padding-bottom: 2.5em;
   background: $body-background;
   font-family: 'Lato', sans-serif !important;
+  font-weight: 300;
 
   @include breakpoint(920px) {
     padding-right: 460px;
   }
 
   .masthead {
-    margin-bottom: 2.5em;
-    margin-left: -1em;
+    padding: 2.5em;
+    padding-top: 0;
+
+    .masthead-heading {
+      padding-top: 4px;
+      font-size: 1.1em;
+      font-weight: 400;
+      color: $gray;
+
+      &:hover {
+        color: $gray-dark;
+      }
+    }
   }
 }