Stick H1 at top of page on conversation view

You’ll quite often be landing half way down this page. So the context
afforded by being able to see the phone number gives you some
reassurance that you’ve landed in the right place.

app/assets/stylesheets/components/sms-message.scss

@@ -68,8 +68,8 @@ $tail-angle: 20deg;
 
   &:focus {
     outline: none;
-    padding-top: 20px;
-    margin-top: -20px;
+    padding-top: 120px;
+    margin-top: -120px;
   }
 
 }

app/templates/views/conversations/conversation.html

@@ -8,9 +8,9 @@
 
   <div class="dashboard">
 
-    <div class="bottom-gutter">
+    <div class="bottom-gutter js-stick-at-top-when-scrolling">
       <h1 class="heading-large">
-        07900 900 123
+        {{ user_number }}
       </h1>
     </div>
     {% for message in conversation %}