added sub_categories to questions
Merge pull request #1 from certifiedloud/master

merging master and dev branches
Merge pull request #10 from certifiedloud/dev

Added support for Sub-Categories
fixed invalid html in question.html template
adjusted Sub_Category class to SubCategory, included some basic tests for subcategory
Merge pull request #11 from certifiedloud/dev

fixed invalid html in question.html template
updated readme with contributors section and updated features certifiedclouds commits
Merge branch 'dev' of https://github.com/tomwalker/django-quiz into dev
tests for image field
unit test that image with the question content as its alt is shown when viewing a question
Merge branch 'master' of https://github.com/tomwalker/django-quiz