Render markup in inline threads on expand/collapse

This was a bug in 3af90ef.

common/static/coffee/src/discussion/views/discussion_thread_view_inline.coffee

@@ -46,6 +46,7 @@ if Backbone?
     expandPost: (event) =>
       @$el.addClass('expanded')
       @$el.find('.post-body').html(@model.get('body'))
+      @showView.convertMath()
       @$el.find('.expand-post').css('display', 'none')
       @$el.find('.collapse-post').css('display', 'block')
       @$el.find('.post-extended-content').show()
@@ -60,6 +61,7 @@ if Backbone?
         $('html, body').animate({scrollTop: postTop})
       @$el.removeClass('expanded')
       @$el.find('.post-body').html(@model.get('abbreviatedBody'))
+      @showView.convertMath()
       @$el.find('.expand-post').css('display', 'block')
       @$el.find('.collapse-post').css('display', 'none')
       @$el.find('.post-extended-content').hide()