Ability to self-update

[phodge]

As a homely user, being on the bleeding edge of everything is important. This includes homely itself, where I want to be able to use all the latest features in my HOMELY.py script and have it work everywhere. Therefore, having homely self-update to the latest version every time I run a homely update would be a valuable feature.

How this might work:

• Make the main homely project just have the CLI script and some APIs for running the CLI script.
• Move the helpers into a homely-core github repo which is separately versioned and contains just the helpers.
• Have homely CLI install the latest homely-core before each run