Added CSS transitions to API Live view

With the browser calculating intermediate color values between frames, the update rate can be further reduced. The interval for updates is now set at 150ms, which seems like a good value for near real-time monitoring of colors.

CPU usage appears to be slightly elevated during transitions, due to the browser calculating *many* intermediate frames, but the baseline CPU usage is even further reduced. Also, with growing browser capabilities, transitions will use less and less power over time.