Topic landing tod

[nsantacruz]

Description

Adds Topic of the Day module to topic landing page

Code Changes

• Adds TopicOfTheDayManager.get_topic_of_the_day(). This is a helper function to get the current topic of the day.
• Adds pytest-django pip package which makes it easier to test django models with pytest. Now any django model objects created in a pytest will be auto-deleted at the end of the test which makes cleanup much easier
• Add topic of the day API
• Factors out from . This makes it easy to render an image with given alt text.