Add autodiscover feature
Add documentation about autodiscover
Add issue #12 improvement
Add new documentations
Bump version
Add model info in permission logic instance
Add GroupInPermissionLogic
Implement StaffPermissionLogic
Add tests for StaffPermissionLogic
Add StaffPermissionLogic
Improve the GroupInPermissionLogic
Add default permission of StaffPermissionLogic
Improve documentation
Bump version
Stop calling `autodiscover()` at `__init__.py`

It will raise if the `permission` is loaded before any installed
application because the model have not installed yet.
This behavior is quite miss-leadable thus I decied to stop calling the
`autodiscover` function automatically.
Update the README
Bump version
Add has_module_perms to fix issue #16
Merge pull request #18 from lambdalisue/support_has_module_perms

Add has_module_perms to fix issue #16
Change returning value to fix issue #17