Updated docs/emacs

  * emacs.org: small enhancement, move key (re)binding from auctex to
    keybinds, and change keybind for cdlatex;
  * emacs.d/auctex-us.el, emacs.d/keybinds-us.el: updated.

Signed-off-by: Vladimir Lomov <lomov.vl@gmail.com>