Transitioning to support RGBA color

The necessary color math to make this work has now been implemented. Now
I just need to refactor into a more sane buffering scheme to get the
performance I need to write to the strip with appropriate timing.
Refactored into OOP

Each segment is now individually addressable. RGBA color is now fully
supported as well.
Restored the sequence functionality

I might eventually want to move the sequence implementation out of the
Strip class (even if only for the sake of keeping the library as small
as possible), but this is fine for now.