Add tox to test/requirements.txt (#698)
Add tox to test/requirements.txt (#698)

* Add tox to test/requirements.txt

To be accordint to the documentation, add tox into requirements.

Closes: #697

Co-authored-by: Adrián Chaves <a1b909ec1cc11cce40c28d3640eab600e582f833@chaves.io>
scrapinghub/dateparser