Nut for Linear stepping motor.

The last Y-axis moving test was not good as following link.
http://www.thingiverse.com/thing:106254

It was too slow, noisy, and non straightness of lead screw.
In addition, the wiring of motor was wrong.

I fixed the straightness of lead screw using by dial gauge.
I re-designed the nut of lead screw, and it replaced instead of the backlash adjusting nuts as following link.
http://www.thingiverse.com/thing:98894

Marlin firmware and Cura used for moving test.
I've setted the def