Django-rest-knox

- Bugfix: invalid token length does no longer trigger a server error
- Extending documentation

**Please be aware: updating to his version requires applying a database migration**

- Introducing token_key to avoid loop over all tokens on login-requests
- Signals are sent on login/logout
- Test for invalid token length
- Cleanup in code and documentation

- Bugfix: invalid token length does no longer trigger a server error
- Extending documentation

- Change to support python 2.7

- Hashing of tokens on the server introduced.
- Updating to this version will clean the AuthToken table. In real terms, this
means all users will be forced to log in again.

- `LoginView` changed to respect `DEFAULT_AUTHENTICATION_CLASSES`

- Initial release