Describe all protocol changes on the Onionoo page
From legacy/trac#21551 (moved): "How do we support the case of different Onionoo hosts running different Onionoo protocol versions? We said we'd include something like "added in version X" and "removed in version Y" in the specification. Sounds totally doable, but maybe in the near future as a subsequent patch." -- "Agreed. Let's keep it simple."