fix on setup.py based on grigorescu/Brownian/18

[vertexclique]

Fix for installation dependency grigorescu/Brownian/18

[grigorescu]

First off, thanks for your updates. I appreciate the help. :-).

Can you tell me a bit more about why the setup.py change is needed? Is it breaking something with your installation?

I try to avoid putting specific versions in setup.py unless that version actually is required. If someone has an older version of pytz installed, I don't want to force them to upgrade unless that version won't work.

[vertexclique]

I tried on linux and macos and yes pytz is not using general versioning convention because of that it is failing at this stage.
I already understood that you don't want to use specific versions but for a later release (or if I fork and carry on putting bricks on this project) this will be much more good way I think.
And thanks for info about build tests I want to develop this project as a fully reliable on elasticsearch because of that I'm interested. Thanks for your kindness and deemed my commits.