SCAD UPC-E Barcode

This is an openscad script to generate UPC-E barcodes

* barcode = this is the 6 digit barcode
* height = the height of the physical object
* thickness = the thickness of the bars
* stretch = This is how tall you want the object to be
* inverse = will make the "spaces" the solid (good when a darker background is used)
* 0 is deafult of no, 1 means yes

Usage:
```
use

barcode(654321,10,2,1,0);
```