* Remove code with side effects from main When running tests withy pytest, some modules execute code in main scope and open plot or browser windows. Moves such code under `if __name__ == "__main__"`. * fixup! Format Python code with psf/black push
* added sol3.py for problem_20 * added sol4.py for problem_06 * ran `black .` on `\Python`
* fuzzy operations added * fuzzy inference system added * unnecessary files removed * requirements added * Modified requirements for travis ci * Modified requirements for travis ci * Add scikit-fuzzy to requirements.txt