Fold new div-by-4 brightness code into Candle

By dividing by 4 rather than 3, we save code space and run faster. We
perfected this in the LED Test side project, so now it is time to bring
that code into the Ognite firmware.

Old size: 3140 bytes
New Size: 3122 bytes

More info:
http://ognite.wordpress.com/2013/12/11/when-more-code-is-less-code/