- use BASH read's prompt capability + use $REPLY rather than polluting
  variable space + use -n var-is-not-empty test flag instead of negating the -z
  var-is-empty flag
Use read -s (noecho) and -p message to ask for passphrase
Replace destroy() with instructions on how to remove a container as it wasn't working anyway.
Make /tmp actually be temporary (tmpfs).
Merge pull request #53 from specing/misc_fixes

Misc fixes (readline, destroy, tmpfs mount, etc.)