Changes

#make a live ubuntu usb disk in os x. [http://www.ubuntu.com/download/desktop/create-a-usb-stick-on-mac-osx directions]

#IN OSX: attach your new portable drive, partition it as an OSX Extended Journaled drive.

#IN UBUNTU: start install. select "something else", create three partitions (boot, root, and swap), leaving existing partition from OSX.

#Install Refind to first partition.