Add compatibility for recent HA versions

[syssi]

2018-12-30 22:04:21 ERROR (MainThread) [homeassistant.loader] Error loading custom_components.switch.flux++. Make sure all dependencies are installed
Traceback (most recent call last):
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/loader.py", line 92, in get_component
    module = importlib.import_module(path)
  File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 986, in _gcd_import
  File "<frozen importlib._bootstrap>", line 969, in _find_and_load
  File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 673, in exec_module
  File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
  File "/home/homeassistant/.homeassistant/custom_components/switch/flux++.py", line 26, in <module>
    from homeassistant.components.light import (
ImportError: cannot import name 'turn_on'