0.17.1: changed to voxel-texture 5.2 to resolve texture issues

the voxel train keeps on chugging!

this update resolves the seam issue shown in the screenshot:

![ve-17-seams](https://f.cloud.github.com/assets/768409/427572/04232498-ade9-11e2-8214-a1f3a4808008.png)

Thanks!