Entitled

Add the ability to pass the entire type, not just an instance of the type, when checking permissions.
Useful for rules that are not necessarily bound to a specific instance but to the type itself, such as creation rules.

**Full Changelog**: https://github.com/xefi/python-entitled/compare/0.3.0...0.4.0

Bringing some classes into the 'entitled' namespace for import convenience

- Some additional refactors and cleanup of syntax
- Rework of the 'grants()' function

- Additionnal unit tests (reaching 90% coverage)

Refactor of rules/policies creation