I'm Jean-Paul, the creator of Fire CI (https://fire.ci). I've been a dev for 10 years and building Fire CI for the past 6 months.
Fire CI is a server that runs local builds in Docker on your own computer. It uses an installable agent to broker the builds with GitHub and also co-ordinates builds between your local server and other members of your team (optional).
It's fast because there is no queueing and a tiny piece of your computer is more powerful than most hosted or rented cloud servers. It's scalable by design: each developer brings his own computing power.
And IMHO the experience is better: the build is local so you get logs and results as fast as it gets. It's also fully integrated to GitHub so build statuses and logs are also available there (almost in real time).
I've been testing Fire CI for a few months with some amazing beta users. I've applied the incredibly helpful feedback I've got and made a ton of improvements and additions. Today is launch day! (but still in beta!)
I'd love to hear your thoughts and answer any questions you may have. Drop a line here or at firstname.lastname@example.org.