Slotscheck

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- Extension modules are now traversed.
- Small tweaks to documentation.

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- Recommend running as ``python -m slotscheck`` when checking files.
Update pre-commit hook to reflect this.

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- Add Python 3.6 support

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**Breaking changes**

- Strict imports are now the default
- Include/exclude regex patterns now use partial patch (like mypy, isort do).

**Adjustments**

- Clarifications in documentation
- Pre-commit hook uses verbose mode by default

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**Breaking changes**

- Arguments are now file paths. Use the ``-m/--module`` option to scan modules.

**Features**

- Support use as pre-commit hook.
- Multiple modules or files allowed as input.
- Document the types of slot errors.

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- Fix typo in readme.