Kosu

- Notebook kernel is changed to match the current course.

- Improved the appearance of feedback messages, and added emojis.
- Improved the rendering of `info` and `exercise` boxes in notebooks.
- Implemented various CI and development updates.

- Added more parameters to `.kosu.yaml` so you can change which folders assets are both kept in and copied to in the build.
- Added a missing file preventing new projects from being initialized with `init`.
- Added a check that the directory is empty before proceeding with `init`.
- Improved the documentation.

- Documentation synced with software.
- Removed Boto3 as dependency (was breaking CI anyway).
- Added support for older versions of Python.

- Added color to the terminal messages, fixing [7](https://github.com/agilescientific/kosu/issues/7). Thank you to [Arunodhai](https://github.com/Arunodhai) for this enhancement.

- More tests, and demo project now builds.