Stepper Motor Driver v3.0

This is the latest incremental improvement to the RepRap Stepper Motor Driver board. This revision brings some polish and a few new features that are really awesome.

1. For the endstop connectors, we've switched to a smaller footprint 4-pin Molex connector typically used as the audio connector on CDROMs. This brings a few nice features: smaller connector footprint (both connector and cable), cheaper connector cables (by a whole $0.15!) and much less confusing to newbies who may confuse the