Add precommit hooks & tox env to enforce code structure, add azure pipelines

Instead of leveraging hound & travis, add an option for azure pipelines,
which may replace the former in the future.

This also streamlines the contributing guidelines by:
* Adding pre-commit hooks to run isort, black, flake8, mypy
* Adding lint environment to allow checks to be run `tox -e lint`

This also contains a major cleanup to the SmartStrip handling which was due.
After seeing #184 I thought I should push this in as it is for comments before the codebase diverges too much.

pyHS100/smartplug.py

@@ -1,11 +1,12 @@
+"""Module for plugs."""
 import datetime
 import logging
 from typing import Any, Dict
 
 from deprecation import deprecated
 
-from pyHS100 import SmartDevice, DeviceType, SmartDeviceException
 from .protocol import TPLinkSmartHomeProtocol
+from .smartdevice import DeviceType, SmartDevice, SmartDeviceException
 
 _LOGGER = logging.getLogger(__name__)