Bondtech gear case for 3mm

A quick modification to make the gear case suit 3mm filament and the e3d bowden couplings.

The distance between the gears is fixed which seems to work ok for now. I didn't have access to the embedded thread things which were used in the original and also the axle that come with the gears seems too short to be tightened with the screws

Assemble by putting the gear in place and press the axle in to the hole. It should be pretty tight fit. The smaller hole allows the axle to be ejected if ne