Using the Certify site for slides / student-teacher interaction

As used in this class, it didn't really add much. Perhaps it would be better to use it only after the other basics are covered and the class has gained some momentum. The beginnings of classes tend to be chaotic, and Certify seemed to add confusion for something that was otherwise underutilized. Since Certify (or similar) affords the ability for more teacher-student interaction, introducing it later and providing the link via a doc in class' repo might be the way to go.

@githubteacher

No file or test is named. Start by reviewing the repository’s class-materials documentation and any current Certify references; done means deciding whether Certify guidance belongs later in the course and documenting the chosen usage or link.

Written by the indexing model from the issue text.