Add an authentication method based on a temporary token, creates the model and the authentication class
Change string to int in time valid variable
Merge current master to avoid problem in a possible merge to master in a future
Add documentation for the apitoken authentication class
Add user resource to documentation and fix Header description
Merge branch 'token_authentication' of https://github.com/jorgeecardona/django-tastypie

Conflicts:
	docs/authentication.rst
	tastypie/models.py
	tests/core/tests/authentication.py