change 'record media' on assignment submission to be a button

the link really was kind of hard to find

fixes #3227

Change-Id: Ia6ee04e944336f60cd2061ec9a44194c46511e31
Reviewed-on: https://gerrit.instructure.com/2476
Tested-by: Hudson <hudson@instructure.com>
Reviewed-by: Mark Suman <marks@instructure.com>

app/views/assignments/_submit_assignment.html.erb

@@ -465,7 +465,7 @@ var submissionAttachmentIndex = -1;
                     <%= image_tag "media_comment.png" %>
                   </div>
                 </div>
-                <a href="#" class="record_media_comment_link" style="font-size: 1.5em;">Record Media Comment</a>
+                <a href="#" class="record_media_comment_link button" style="font-size: 1.1em;"><%= image_tag "record.gif" %> Record Media Comment</a>
                 <div id="media_media_recording_submission" style="display: none; float: left; width: auto; border: 2px solid #444;">
                 </div>
                 <div class="clear"></div>