add a "load_smartcd" shim to simplify new installs
improve the output of "smartcd show"
smartcd_edit commands operate on "type" not "file"
README improvements
add a "smartcd delete" for convenience
allow bin/smartcd to invoke edit

Soon, "smartcd edit" will accept specifiers such as "--system" to
identify which set of scripts to operate on.  It's probable that you
will need escalated privilege to edit system-wide scripts, and when
invoked as "sudo smartcd ..." you'll lose smartcd from your environment

In this case, bin/smartcd may be invoked instead, and can gracefully
handle the edit, so do so