Review tidy labels

[hadley]

• Remove performance; I think it's actually a repo specific issue
• Adjust colours to be less saturated (e.g. http://tristen.ca/hcl-picker/#/hlc/5/0.35/FCC3BB/EAC492)
• Rename docs to documentation?

[hadley]

Demo at https://github.com/hadley/test/labels