Lisp aesthetics

[basil-conto]

These changes:

• should be backward-compatible until at least Emacs 23;
• should not change any functionality of the package; and
• try to simplify or make more idiomatic the Lisp code itself.

I have tried to keep each commit as atomic and their message as descriptive as possible, so I recommend reviewing each one individually.

[clarete]

This is really nice! Thanks for all these improvements!!!