Duplicate hooks shown just because they contain the same word

[StephaneCapponi]

If there is two different hook that contain the same word, even if they are different throw an error:

socon.core.exceptions.ImproperlyConfigured: 'foo' already exists. Duplicates:
...

Issue is here: https://github.com/socon-dev/socon/blob/c808a324500e5da915621de05a6f9c60b38c9cb8/socon/core/manager.py#L319 Instead of "hook_name in n" it should be "hook_name == n"