* Fix plugin names for collection plugins.
Add an integration test to verify plugin __name__ is correct for collection plugins.
* Fix collection loader PEP 302 compliance.
The `find_module` function now returns `None` if the module cannot be found. Previously it would return `self` for modules which did not exist.
Returning a loader from `find_module` which cannot find the module will result in import errors on Python 2.x when using implicit relative imports.
* add changelog
* sanity/units/merge fixes
