Parametric Riser for Thomas/Brio-compatible Wooden Trains

Parametric module to create a riser to support sloped wooden train tracks for Thomas- and Brio-compatible wooden train sets. Parameters allow for multiple heights based on standard measurements
 
To render this shape, you will need [tracklib.scad](http://www.thingiverse.com/thing:216915) installed in the same directory as this file, or the [dotscad/trains](https://github.com/dotscad/trains) repository cloned in its entirety (which will include this file and tracklib.scad).
 
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