" You need to install the Arduino IDE from http://arduino.cc/en/Main/Software to acquire the correct driver files." Quote from makerGear wiki.

Good work nice print.

You are not making full contact with the end switch hence the bouncing. There is a slot in the spider mount plate that allows an adjustment
of the nylon bushing that makes contact with the y end-stop switch, just loosen the bolt and move it until makes better contact with the
micro-switch.