Allure-pytest plugin for pytest html report

Currently, tox generates reports directly to the terminal. It will be very difficult to read the report when the test list is long and multiple failures happen.

allure-pytest is a good plugin for pytest to save the log, organize and show the report through an html page.

By running "python3 -m pytest --alluredir=allure-report/", reports are saved in the allure-report folder. Later, html page can be created by running "allure serve tests/allure-report".