make Emacs bindings that stick around

 This is a package for GNU Emacs that can be used to tie related commands into
 a family of short bindings with a common prefix - a Hydra. Once you summon
 your Hydra through the prefixed binding (the body + any one head), all heads
 can be called in succession with only a short extension. Hydra can be vanished
 with any binding that isn't the Hydra's head (and that binding will call a
 proper command too). This makes the Hydra very seamless, it's like a minor
 mode that disables itself automagically.