add info in the readme how one may run tests

[Mateusz Konieczny]

currently, at least for me, it is not obvious

[Hong Minhee (洪 民憙)]

Sorry for the late response. We use tox or detox to run tests. Tox purposes to run a test suite for multiple Python interpreters (multiple versions and multiple VMs like CPython and PyPy). Detox is a parallelized version of tox. If a tox is installed in your system it's easy to run tests:

tox