Update pip-tools to 2.0.1

[pyup-bot]

This PR updates pip-tools from 1.11.0 to 2.0.1.

Changelog

2.0.1

Bug Fixes:
- Added missing package data from vendored pip, such as missing cacert.pem file. Thanks vphilippon

2.0.0

Major changes:
- Vendored `pip` 9.0.3 to keep compatibility for users with `pip` 10.0.0
([644](https://github.com/jazzband/pip-tools/pull/644)). Thanks vphilippon

Features:
- Improved the speed of pip-compile --generate-hashes by caching the hashes from an existing output file
([641](https://github.com/jazzband/pip-tools/pull/641)). Thanks justicz
- Added a `pip-sync --user` option to restrict attention to user-local directory
([642](https://github.com/jazzband/pip-tools/pull/642)). Thanks jbergknoff-10e
- Removed the hard dependency on setuptools
([645](https://github.com/jazzband/pip-tools/pull/645)). Thanks vphilippon

Bug fixes:
- The pip environment markers on top-level requirements in the source file (requirements.in)
are now properly handled and will only be processed in the right environment
([647](https://github.com/jazzband/pip-tools/pull/647)). Thanks JoergRittinger

Links

• PyPI: https://pypi.org/project/pip-tools
• Changelog: https://pyup.io/changelogs/pip-tools/
• Repo: https://github.com/jazzband/pip-tools/

[coveralls]

Coverage remained the same at 70.137% when pulling c1e813f on pyup-update-pip-tools-1.11.0-to-2.0.1 into bda205f on master.