Feature/add tests capabilities

[XavierBerger]

Hello,

Here is a quite massive pull request...

This pull request is containing additional test capabilities I used to test my appdaemon applications (ref my github for application and tests) : cancel_listen_state,listen_event, fire_event, immediate in callback, run_in

I did add also the build environment I used which is VSCode Server inside HA web interface.

The code has been validated by blake and flake8 as in this repository and also with pylint since I use it in all my python dev.
The code is fully tested with a coverage of 100%.

I hope you will find this pull request interesting. Anyway thanks for you job which allow me to have a coverage of 100% on my code.

[TechnicallyShaun]

@nickw444 did you give any consideration to this PR?
Super interested in the set_current_time and advance _time methods

@XavierBerger do you have a public pip install package for a fork of this improvement?

[XavierBerger]

@ssmithy I don't plan to publish a fork of this repo on PyPi.

[TechnicallyShaun]

Appreciate the ping back - thank you 🙂