Installs 2.1.2 on debian/ubuntu via checkinstall so it's in your package manager and you can remove it.
Quick install:
curl -L https://gist.github.com/mortik/4ea0208b1688097c9549/raw/855840025891f3b7e764bf720026072104c5c3bd/ruby-2-install-debian.sh | bash -s