change ruby-build instructions to match setup.sh
change ruby-build instructions to match setup.sh

use ruby-1.9.3-p392, jruby-1.7.2 and rubinius-2.0.0-rc1 to match scripts/setup.sh
regularfry/chruby,ngpestelos/chruby,kbrock/chruby,kbrock/chruby,rstacruz/chruby-fish,eunomie/chgo,ilikepi/chruby,ilikepi/chruby,JeanMertz/chruby-fish,regularfry/chruby,JeanMertz/chruby-fish,eunomie/chgo,postmodern/chruby,rstacruz/chruby-fish,ngpestelos/chruby,postmodern/chruby