Update pip-tools to 1.8.2

[pyup-bot]

There's a new version of pip-tools available.
You are currently using 1.8.0. I have updated it to 1.8.2

These links might come in handy: PyPI | Changelog

Changelog

1.8.2

• Regression fix: editable reqs were loosing their dependencies after first round (476)
  Thanks mattlong
• Remove duplicate index urls in generated requirements.txt (468)
  Thanks majuscule

1.8.1

• Recalculate secondary dependencies between rounds (378)
• Calculated dependencies could be left with wrong candidates when
  toplevel requirements happen to be also pinned in sub-dependencies (450)
• Fix duplicate entries that could happen in generated requirements.txt (427)
• Gracefully report invalid pip version (457)
• Fix capitalization in the generated requirements.txt, packages will always be lowercased (452)

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

Happy merging! 🤖