Micro gearmotor adapter for Spider Rover

I couldn't find the recommended motor here in the USA without paying for international shipping. So I sourced a different motor, which is a [150:1, 175 RPM micro gearmotor](https://www.sparkfun.com/products/12205). You may want to try a different motor, but this one seems to work well.

I had to create a special mount and change the pulley a bit to support this motor, which I've uploaded.