Update tox to 3.5.2

[pyup-bot]

This PR updates tox from 3.4.0 to 3.5.2.

The bot wasn't able to find a changelog for this release. Got an idea?

Links

• PyPI: https://pypi.org/project/tox
• Docs: https://tox.readthedocs.org/

[coveralls]

Pull Request Test Coverage Report for Build 32

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 85.106%

---

Totals
Change from base Build 26:	0.0%
Covered Lines:	80
Relevant Lines:	94

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 32

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 85.106%

---

Totals
Change from base Build 26:	0.0%
Covered Lines:	80
Relevant Lines:	94

---

💛 - Coveralls

[pyup-bot]

Closing this in favor of #12