Convert all `jjin-*-map` to pretty-hydra

[Jonathan Jin]

No real reason not to do this, plus you get all the benefits of hydra.

.emacs.d/README.org

Lines 506 to 518 in deb7e64

 #+BEGIN_SRC emacs-lisp 
   (define-prefix-command 'jjin-vc-map) 
   (bind-key "C-c v" 'jjin-vc-map) 
  
   (define-prefix-command 'jjin-comment-map) 
   (bind-key "C-c c" 'jjin-comment-map) 
  
   (define-prefix-command 'jjin-term-map) 
   (bind-key "C-c t" 'jjin-term-map) 
  
   (define-prefix-command 'jjin-buffer-map) 
   (bind-key "C-c b" 'jjin-buffer-map) 
 #+END_SRC