Fan duct for RepRapPro Mendel

This piece is a fan mount/duct/nozzle for the RepRapPro Mendel with the updated x-carriage design. It mounts to a head slot next to a print head whose nozzle is to be cooled. The nozzle directs the air flow just below the extrusion point.

**UPDATE**: added a version which mounts opposide to the head, as opposed to next to it.