Add student total playtime to ClassroomView

app/styles/courses/classroom-view.sass

@@ -2,6 +2,9 @@
   #main-button-area
     .btn
       margin-left: 10px
+      
+  #student-stats-row
+    margin-bottom: 20px
   
   .progress
     margin-bottom: 5px

app/templates/courses/classroom-view.jade

@@ -35,8 +35,13 @@ block content
     
     h2= user.broadName()
     - var lastPlayedString = view.makeLastPlayedString(user);
-    if lastPlayedString
-      p Last Played: #{lastPlayedString}
+    - var playtime = view.makePlaytimeString(user);
+    if lastPlayedString || playtime
+      #student-stats-row.row
+        if lastPlayedString
+          .col-sm-6 Last Played: #{lastPlayedString}
+        if playtime
+          .col-sm-6 Playtime: #{playtime}
       
     - var paidFor = user.get('coursePrepaidID');
     for courseInstance in view.courseInstances.models

app/views/courses/ClassroomView.coffee

@@ -122,6 +122,11 @@ module.exports = class ClassroomView extends RootView
     campaignLevel = campaign.get('levels')[levelOriginal]
     return "#{campaign.get('fullName')}, #{campaignLevel.name}"
 
+  makePlaytimeString: (user) ->
+    playtime = _.reduce user.sessions.pluck('playtime'), (s1, s2) -> (s1 or 0) + (s2 or 0)
+    return '' unless playtime
+    return moment.duration(playtime, 'seconds').humanize()
+
   onClickAddStudentsButton: (e) ->
     modal = new InviteToClassroomModal({classroom: @classroom})
     @openModalView(modal)