Make aspectlib raise better exceptions.
Use six.
Fix issues with closing generators in an Aspect. Now exceptions from the cutpoint function are properly reraised.
Update changelog, spelling.
Actually reraising is not needed.
Revert "Use six."

This reverts commit eb7ee81086725c3e40ff2dae7a13a754514bdcf8.
Add partial support for advising generators.
Implement coroutine handling ... somewhat ...
Fix the test.
Fixed various issues in the generator support.