emacs: configure elisp-mode in one place
emacs: configure elisp-mode in one place

Also add some handy keybindings for hacking on lisp.

The keys here are based on John Wiegley's configuration available at
https://github.com/jwiegley/dot-emacs/blob/078e38/init.el#L453-L465 and
Sebastian Wiesner's configuration available at
https://github.com/lunaryorn/.emacs.d/blob/5c10e7/init.el#L2046-L2053.

omajid/config