feat (switch): add support for the lifx switch

[bradrees]

This PR adds support for the Lifx Switch.

I've added tests and tested on my switches at home, and it all seems to work.

Thanks to the work done by @Shakesbeard and @ristomatti

Resolves #38

[ristomatti]

Thank you for the contribution! I'm very busy at the moment (working on a huge and blocker code refactor at work) so I can't promise when I will be able to review this. I'll be snoozing the email notification until I get time to properly check this.

I did a quick glance though and it seemed the changes seem to align with the codebase. Only biggest issue is about how well this fits to the current API. A switch/relay cannot easily be seen as a light (even though it could be toggling a light).

It would help if you could either:

• Update the README, while trying to figure out how to describe the new API in a way it doesn't sound awkward
• Come up with a suggestion how we could adapt the code structure to have an object device which would then be inherited by light and switch (or relay).

The latter would be preferred but as it'd be a lot of work, I'm not sure if I want it to be a thing to prevent people from using the library with their switches.

[ristomatti]

Just to update - I've not forgot about this. 😬

[bradrees]

Hi, I have added some documentation and have been using this with Homebridge for the last 7 or so months, it works really well and is a big improvement over the standard lifx app. It's all stable and works every time.

It would be great to get this merged in, it really improves my setup at home.

Thanks!

[ristomatti]

Can't test this but can't spot any issues either. The code and docs fit nicely in the existing code style 👍. I'll take a leap of faith and publish a new minor release. Thanks you for the contrib and sorry it took ages to review!