Update pip-tools to 1.9.0

[pyup-bot]

There's a new version of pip-tools available.
You are currently using 1.8.2. I have updated it to 1.9.0

These links might come in handy: PyPI | Changelog

Changelog

1.9.0rc1

Features:

• Added ability to read requirements from setup.py instead of just requirements.in (418). Thanks to tysonclugg and majuscule.
• Added a --max-rounds argument to the pip-compile command to allow for solving large requirement sets (472). Thanks derek-miller.
• Exclude unsafe packages' dependencies when --allow-unsafe is not in use (441). Thanks jdufresne.
• Exclude irrelevant pip constraints (471). Thanks derek-miller.
• Allow control over emitting trusted-host to the compiled requirements. (448). Thanks tonyseek.
• Allow running as a Python module (461). Thanks AndreLouisCaron.
• Preserve environment markers in generated requirements.txt. (460). Thanks barrywhart.

Bug Fixes:

• Fixed the --upgrade-package option to respect the given package list to update (491).
• Fixed the default output file name when the source file has no extension (488). Thanks vphilippon
• Fixed crash on editable requirements introduced in 1.8.2.
• Fixed duplicated --trusted-host, --extra-index-url and --index-url in the generated requirements.

Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.

Happy merging! 🤖