Add Tough Love Arena to README.md

[mpaulweeks]

What is the purpose of this pull request? (put an "X" next to item)

[x] Documentation update [ ] Bug fix [ ] New feature [ ] Other, please explain:

What changes did you make? (Give an overview)

Added link to Tough Love Arena

Which issue (if any) does this pull request address?

*Your app here! - send a PR!*

Is there anything you'd like reviewers to focus on?

n/a