Add Emacs mode (fix #81)

Can you test whether this works on your machine, Paolo?

Stuff that should work:

 1. copy-paste the snippet from the README.me to your .emacs, restart emacs, emacs should not break.
 2. visit UU.lpts, the mode should load, nothing should break, you should get syntax highlighting.
 3. Press C-c C-l. Emacs should ask you for a project directory.
 4. Then emacs should ask you for a PTS instance. There should be tab completion.
 5. Then emacs should call pts for you.
 6. Visit UU/T/cps.lpts and press C-c C-l. This time, emacs should guess the project directory from the module statement and only ask you for the instance.