enable to set color per poly.

Hi, I'm very happy to use your code!

I'm operating laser in ILDA, and developed inteactive laser in DMX.
So I'm very happy to find this.
But I want to set color per poly, so I add this feature, though I add little code.

I sent my pull request if it is useful for some developers.
I'm happy if you accept my pull request.

If you want to change color, you should set new color to ildaFrame.params.output.color before call addPoly().


sample code:
ofFloatColor color = ofFloatColor(ofRandom(1.0f), ofRandom(1.0f), ofRandom(1.0f), 1);
ildaFrame.params.output.color = color;  // set new color
ildaFrame.addPoly(); // add new poly

Thanks,
Mitsuru