Breaking changes in Arrow library

[Hugo-Polloli]

Hi,
Every instance of using dates from the Arrow library might be subject to breaking changes as per arrow-py/arrow#832.

The most blatant one I've run into stems from point 2 and 3 of aforementioned list of breaking changes. See

cassiopeia/cassiopeia/core/match.py

Line 285 in 5c516e5

begin_time = begin_time.timestamp * 1000

and others.

There could either be fixed using a requirement such as arrow<1.0.0 or update Cassiopeia according to said changes. I will try to go over those and if possible provide a PR.

Edit: last commit is just about this version pin, somehow my pip install didn't care, I will still attempt to provide a PR fitting Arrow changes and removing the need of a version pin