Add boiler `AUTO` mode and more

[fmartinou]

Hi @mrwiwi ,

At the first time, I just wanted to add a new boiler mode (AUTO). but one thing led to another and... I've finally reworked more than that 😄.

I added:

• Boiler AUTO mode (of course 😂 )
• Multi-arch Docker images (arm/v6, arm/v7, arm64/v8, amd64)
• Lighter Alpine based docker images (~55MB instead of ~120MB)
• Travis CI
• Python PEP8 code style enforcement
• Default values allowing to connect to MQTT as anonymous without having to set any extra environment variable
• Some documentation I found useful

Basically, anywhere you can read fmartinou in the commited files, you should rename with mrwiwi. If you want to set-up the Travis CI, you need to:

1. create a free Travis account
2. set 2 variables (DOCKER_USERNAME and DOCKER_PASSWORD with your Docker hub credentials) (I can guide you for this part if you wish)

Feel free to accept or ignore my work or just the parts you're interested in (I will not take offence) 😄 .

PS: FYI, in the meantime, I'm using my fork and the resulting images published here

Bye!