Merge pull request #633 from MITx/feature/ichuang/histogram-try-catch

put try-catch around histogram coffeescript code

lms/static/coffee/src/courseware.coffee

@@ -14,4 +14,9 @@ class @Courseware
     XModule.loadModules('display')
     $('.course-content .histogram').each ->
       id = $(this).attr('id').replace(/histogram_/, '')
-      new Histogram id, $(this).data('histogram')
+      try
+        histg = new Histogram id, $(this).data('histogram')
+      catch error
+        histg = error
+        console.log(error)
+      return histg