added ie warning banner to courseware; displayed by ie conditional stylesheet

lms/static/sass/course/layout/_courseware_header.scss

@@ -169,3 +169,20 @@ header.global.slim {
     letter-spacing: 0;
   }
 }
+
+.ie-banner {
+  display: none;
+  max-width: 1140px;
+  min-width: 720px;
+  margin: auto;
+  @include border-radius(0 0 3px 3px);
+  background: #f4f4e0;
+  color: #3c3c3c;
+  padding: 5px 20px 8px;
+  font-size: 13px;
+  text-align: center;
+
+  strong {
+    font-weight: 700;
+  }
+}

lms/static/sass/ie.scss

@@ -151,3 +151,7 @@ header.global ol.user > li.primary a.dropdown {
 .dashboard .my-courses .my-course .cover .arrow {
   display: none;
 }
+
+.ie-banner {
+  display: block !important;
+}

lms/templates/navigation.html

@@ -79,9 +79,10 @@ site_status_msg = get_site_status_msg()
       </li>
 % endif
     </ol>
-  </nav>
   %endif
+  </nav>
 </header>
+<div class="ie-banner"><strong>Warning:</strong> Your browser is not fully supported. We strongly recommend using <a href="https://www.google.com/intl/en/chrome/browser/" target="_blank">Chrome</a> or <a href="http://www.mozilla.org/en-US/firefox/new/" target="_blank">Firefox</a>.</div>
 
 %if not user.is_authenticated():
   <%include file="login_modal.html" />