added note to README to indicate this is for v3.0.0-rc.1
added note to README to indicate this is for v3.0.0-rc.1

mosoft521/javascript-state-machine,jakesgordon/javascript-state-machine,QuentinRoy/javascript-state-machine,mosoft521/javascript-state-machine,QuentinRoy/javascript-state-machine,jakesgordon/javascript-state-machine