Adding comment about div that can't be removed.

Also fixing Meta class being defined twice in one model

openedx/features/course_experience/templates/course_experience/dates-summary.html

@@ -2,6 +2,8 @@
 from django.utils.translation import ugettext as _
 %>
 <%page args="course_date" expression_filter="h"/>
+## The date-summary-container div must stay here because it is used in our
+## mobile app javascript code as a selector.
 <div class="date-summary-container">
     <div class="date-summary date-summary-${course_date.css_class}">
         <div class="left-column">