Added reference to rvm-mini

Inspired by rvm (http://rvm.io) we created a very small ruby installer and runtime environment based on binaries of rvm - I call it little rvm brother. Conceptional changes were done based on discussion about vulnarables with @mpapis. Details at: https://github.com/TomFreudenberg/rvm-mini/issues/2

Would be nice if you could append the references to the list.