* Factored out ratio computation into a separate function for testability
* Extended ratio function to use python or bc, whichever is available
* Changed required ratio from 10x to 10% to handle smaller disk sizes
* Added tests for the ratio function in fdisk_test.sh
* Changed the run line from "bash -eu" to just "bash -u" to not exit immediately
  on non-zero exit code, because fdisk(1) exits with a non-zero exit code, and
  we want to run the reboot automatically