style the guided discussion text so it is boxed like the instructions text.

common/lib/xmodule/xmodule/css/annotatable/display.scss

@@ -25,6 +25,7 @@ $body-font-size: em(14);
     border-top: 1px solid $border-color;
     margin-top: .5em;
     padding-top: .5em;
+    @include clearfix;
   }
 }
 

lms/templates/annotatable.html

@@ -22,7 +22,8 @@
             Guided Discussion
             <a class="annotatable-toggle annotatable-toggle-annotations" href="javascript:void(0)">Hide Annotations</a>
         </div>
+        <div class="annotatable-section-body annotatable-content">
+            ${content_html}
+        </div>
     </div>
-
-	<div class="annotatable-content">${content_html}</div>
 </div>