Make Python Package

[colematt]

This issue defines the plan for breaking this code apart into a proper Python package.

The directory structure will be thus:

pyotp/
├── docs
│   ├── rfc4226.pdf
│   ├── rfc6238.pdf
│   ├── test.png
│   ├── totp-process.png
│   ├── totp-sequence.graffle
│   └── totp-slides.pdf
├── LICENSE
├── pyotp_pkg
│   ├── __init__.py
│   ├── __main__.py
│   ├── otp.py
│   ├── provision.py
│   └── test.py
└── README.md

• Add directory/file structure
• Split otp.py
• Move demo into standalone code importing pyotp module.