Eustathios Z-axis Support

Remix of Eric Lien's [Eustathios V2 Spyder](https://github.com/eclsnowman/Eustathios-Spider-V2) Z-axis leadscrew support. There are a few minor changes to improve the fit with the ball screw I used. If I had the ball screw milled to the specs in the BOM, I would not have had to make these changes, so I'd recommend doing that and using the original parts if possible. There is now a parts listing for a [ball screw](http://www.aliexpress.com/store/product/Best-quality-1pc-Ball-screw-SFU1204-L425mm-1pc-RM1204-Ballscrew-Ballnut-standard-processing-for-CNC-BK10/920371_32592258963.html) that is compatible with the original parts.

**Printer:**
-- [RigidBot](http://thrinter.com/rigidbot-modifications/)

**Filaments:** (full list can be found on [thrinter.com](http://thrinter.com/filaments))
-- [Hatchbox Transparent Black ABS](http://thrinter.com/walters-filament-collection-abs/#hatchbox-tblack)