I believe apm must have been buggy - example output that I found online
showed `tr` was mangling paths with spaces in it. Should be fixed.
Also, use dscl on OS X in __fish_complete_users.fish like
__fish_print_users.fish already does.
Currently fish doesn't recognize toor as special. However, it's likely
that on BSD systems, fish shell will be used on toor, not on root (toor
is an intentionally existing account to use more advanced shell on, like
shell).