Add support for SetExtendedColorZones

[samuelgoodell]

This adds support for the new(-ish) SetExtendedColorZones (510) message type for compatible products (e.g. LIFX Z Strip, LIFX BEAM).

See the README.md diff for an example of how this works. I tried to work within the conventions of your codebase.

Sam

[samuelgoodell]

Hi @futomi, would you be open to reviewing or discussing this PR?

Sam

[samuelgoodell]

Hi @futomi, I was circling back to this and noticed you had some activity on this remote again. I updated my pull request here to resolve the small merge conflict.

Would you be open to including this? The SetExtendedColorZones functionality is a huge benefit for consumers of the library, it allows setting a range of colors on a multi-zone light with a single request, enabling huge performance gains with e.g. animated effects.

I have included documentation for the new method consistent with yours in the README.