Add TopicTests and Topic class to compile.
Add Topic initializer with default value.
Add topic property to test class. Refactor Topic initializers.
Add QuestionTests and Question to fulfill Topic need for list of Questions.
Add addQuestion to Topic and sort recentQuestions
Remove questions after 20.
Merge pull request #1 from SixFiveSoftware/tests/add_topic_tests

Tests/add topic tests