Conflicting info on Rails versions supported

[brandonzylstra]

The README states that

This gem is for Rails 4+ only. It supports MySQL (including the mysql2 gem), PostgreSQL and SQLite.

but the repo's tagline states

Adds SQL analysis and debugging information to Rails 3.x, 4.x apps.

I suspect the README is correct and the tagline is false, but

1. I would like to know for sure (as would other users, I'm sure), and
2. Most users are not likely to ever read the README after seeing the tagline, and reading that it only supports ancient versions of Rails.