setBrightness

[TheKitty]

The setBrightness function is very handy (saves power, allows your eyes to stop burning when working, etc.).

I suggest one or more examples shows using this.

[t3chguy]

Examples should definitely use this, or maybe even set the default lower to prevent people which don't know about the brightness of these crazy NeoPixels staring directly into them without setting the brightness lower.

[rtepowers]

I made a PR #67 for this.