Found this awesome Django Toolbar to test times of templates: https://github.com/orf/django-debug-toolbar-template-timings

The lecturer for loop inside the category seems to be the culprit that needs so much rendering time. Could this be because Django does complicated variable lookups?

With the for loop it takes 3000ms:
![with_lecturers](https://cloud.githubusercontent.com/assets/1288339/2819431/8a9edec8-ceee-11e3-8d9b-d5743f1af5a7.png)


and without only a fifth:
![without_lecturers](https://cloud.githubusercontent.com/assets/1288339/2819432/8dc9ca4a-ceee-11e3-8ba7-9a2ef85a0942.png)