Requirement is pinned for python-miio 0.5.3: pytz>=2019.3,<2020.0

[MartinHjelmare]

Describe the bug

• This library supports an integration in Home Assistant.
• The upcoming pip resolver will be more strict in resolving package version conflicts:
  http://pyfound.blogspot.com/2020/03/new-pip-resolver-to-roll-out-this-year.html#what-will-change
• To avoid future issues it would be good if this library would change its pinning to allow any higher version and just set a minimum version.

Thanks for your support of Home Assistant!

Version information (please complete the following information):

• OS: Ubuntu 18.04
• python-miio: 0.5.3

To Reproduce
Steps to reproduce the behavior:

(home-assistant) x:~/Dev/home-assistant/home-assistant$ pip install -r requirements_all.txt
...
(home-assistant) x:~/Dev/home-assistant/home-assistant$ pipdeptree --reverse --packages pytz
...
pytz==2020.1
...
  - python-miio==0.5.3 [requires: pytz>=2019.3,<2020.0]
...

Expected behavior

• To avoid future issues it would be good if this library would change its pinning to allow any higher version and just set a minimum version.