Solidoodle extruder head wobble preventer

This hack keeps the Solidoodle extruder head from wobbling when making rapid Y-Axis movements. It moves the lower teflon retainer block on the X-Axis carriage to a spring loaded arm that keeps the back of the print head from bouncing up. This also keeps prints from being distorted when printing near the back of the print bed, where force from the cable assembly can sometimes tip the print/extruder head.