Airthings Wave Plus Support!!!

Thanks to the excellent work done by @sverrham , sensor.airthings_wave now supports the Airthings Wave Plus!
As an added bonus, @sverrham's refactoring and optimizing of the code has also resolved issue #2

V1.0: Merge pull request #19 from kressir/kressir-patch-1

Bumping to a full release

0.5

Made bluetooth implementation more resilient