More tweaks to width of elements

- SMS message preview gets slightly wider so it lines up with a 4/8
  column
- Edit email box gets wider to match more closely the width of the
  previewed and delivered emails

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

@@ -2,7 +2,7 @@
 .sms-message-wrapper {
 
   width: 100%;
-  max-width: 450px;
+  max-width: 464px;
   box-sizing: border-box;
   padding: $gutter-half $gutter-half $gutter-half $gutter-half;
   background: $panel-colour;

app/templates/views/edit-email-template.html

@@ -15,11 +15,9 @@
 
     <form method="post">
       <div class="grid-row">
-        <div class="column-three-quarters">
+        <div class="column-five-sixths">
           {{ textbox(form.name, width='1-1', hint='Your recipients won’t see this', rows=10) }}
           {{ textbox(form.subject, width='1-1', highlight_tags=True, rows=2) }}
-        </div>
-        <div class="column-three-quarters">
           {{ textbox(form.template_content, highlight_tags=True, width='1-1', rows=8) }}
           {% if current_user.has_permissions([], admin_override=True) %}
              {{ radios(form.process_type) }}