Easier config, more stable, remove threading

In this release I've tried to make the installation process easier. You can now just add the config.json by typing python3 config.py or just run it with python3 schedule.py.

Also I've removed threading, because the Google Calendar API will sometimes give a 401 Error. This will make it a bit slower, but it's less prone to bugs.

I've also fixed some basic mistakes, I started using os.path.join instead of just adding the paths together and hoping it'll work.