Adding a new tidier

[jayhesselberth]

Fork the repository to your own account.

1. Add a header for the dataset (e.g. ## dataset)
2. Add a code bock (e.g. {r} ...)
3. [opt] Add tidying code, ending the block by printing the tidied data
4. [opt] OR print a message that the dataset is already tidy.
5. Re-knit the README.md file to check

Rinse, repeat for next dataset.

Submit a PR.