Anet A8 - Z Endstop Fine Adjustment

Updates 30/07/2017
Uploaded a version with a bigger hole around Z motor shaft, so now it is completely usable for those people willing to use plum couplers. Still has the gap on the inner side, so it's pretty easy to reach the couplers' setscrews with an allen wrench.
Regarding the X motor piece, now it is 2mm wider, and has a slightly shorter stroke, since there's no need of 20+mm stroke for such a precise thing. Additionaly, I moved the holes upwards, because with 3mm glass sheet mine was a