Merge pull request #7 from certifiedloud/master

Added support for figures
Merge branch 'master' of https://github.com/tomwalker/django-quiz
small fix for errors in admin, also added ability to filter subcategories by their parent categories
made quiz.progress.list_all_cat_scores a property, changed quiz.progress.update_score use a question rather than a category as its calling arguement. This is to allow easier integration of tracking subcategory scores (which has not been implemented yet)