Python Paper Enigma

Partially implements paper Enigma found here: http://mckoss.com/Crypto/Enigma.htm

The original motivation to writing this was to be able to generate the Rejewski characteristics quickly. I've neglected a few things to focus on this goal, for example:

• the adjacent rotors don't automatically shift after the cycle is completed.

Example usage:

>>> from enigma import Enigma
>>> e = Enigma()
>>> e.encrypt('ATTACK AT DAWN')
'BZHGNOCRRTCM'