Shortening title of Git tutorial
1. Editing and extending the lesson on testing.
2. Changing the `rectangle_area` function's name (we only need one version in the end).
3. Adding a `border` function for another example.
4. Modifying `ears` to take a `prefix` argument specifying which tests to run.
Adding link to index page
Adding link to Git tutorial
Adding more information to the README file for creating bootcamp home pages