Added generate/validate token methods to django_token_auth

used PyCrypto to perform RSA signing.
added unittests
Added TokenAuthenticationMiddleware and TokenAuthenticationBackend. Added draft of TokenAuthenticatedUser

Middleware checks the token persistance and calls authenticate() methods
Authentication backend is used to perform user authentication by calling validate_auth_token()
TokenAuthenticatedUser represents a user that was build from token data and we don't know
any information about him except of username
Merge pull request #1 from WiserTogether/token_generator

Token generator
Updated docstring
Merge pull request #2 from WiserTogether/auth_middleware

Auth middleware
Small README draft
Merge pull request #3 from WiserTogether/readme

Small README draft
fix setup
Merge pull request #4 from WiserTogether/fix-setup

Fix setup
Merge pull request #3 from WiserTogether/master

Backporting from wiser