Update capturer to 3.0

[pyup-bot]

This PR updates capturer from 2.4 to 3.0.

Changelog

3.0

---------------------------

This is a maintenance release that updates the supported Python
versions, adds a changelog and makes some minor internal changes:

- Added support for Python 3.7 and 3.8.
- Dropped support for Python 2.6 and 3.4.
- Actively deprecate ``interpret_carriage_returns()``.
- Moved test helpers to :mod:`humanfriendly.testing`.
- Include documentation in source distributions.
- Use Python 3 for local development (``Makefile``).
- Restructured the online documentation.
- Updated PyPI domain in documentation.
- Added this changelog.

.. _Release 3.0: https://github.com/xolox/python-capturer/compare/2.4...3.0

Links

• PyPI: https://pypi.org/project/capturer
• Changelog: https://pyup.io/changelogs/capturer/
• Docs: https://capturer.readthedocs.io