[Doppins] Upgrade dependency pip-tools to ==3.0.0

[doppins-bot]

Hi!

A new version was just released of pip-tools, so Doppins
has upgraded your project's dependency ranges.

Make sure that it doesn't break anything, and happy merging!

---

Upgraded pip-tools from ==2.0.2 to ==3.0.0

Changelog:

Version 3.0.0

Major changes:

• Update pip-tools for native pip 8, 9, 10 and 18 compatibility, un-vendoring pip to use the user-installed pip (#657](https://github.com/jazzband/pip-tools/pull/657) and [#672 (https://github.com/jazzband/pip-tools/pull/672)).
  Thanks to @techalchemy, @suutari, @tysonclugg and @vphilippon for contributing on this.

Features:

• Removed the dependency on the external library first (#676 (https://github.com/jazzband/pip-tools/pull/676)). Thanks @jdufresne

[coveralls]

Coverage remained the same at 53.526% when pulling b1b1218 on doppins/pip-tools-equals-3.0.0 into 78a1574 on master.