Dev dependencies should be separated from normal dependencies

[phiresky]

Right now, the setup.py file specifies that the dependencies should be loaded from requirements.txt. But the requirements.txt file specifies things like black, which are not actually needed when installing wacz as a dependency.

This means that if you have a program that needs on a current version of black you cannot add wacz as a dependency due to soemthing like this error from pip:

ERROR: Cannot install <depender> because these package versions have conflicting dependencies.
The conflict is caused by:
    black 22.1.0 depends on click>=8.0.0
    nltk 3.7 depends on click
    wacz 0.3.2 depends on click<7.2.0 and >=7.1.1

I don't know what the most "pythonic" solution to this is (except using pyproject.toml instead of setup.py), but in general wacz should not depend on black as a library.