Added an error-check and corrected parameter passing#12

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AlanFord wants to merge 3 commits intotinylabs:masterfrom

AlanFord:master

Commits on Feb 21, 2018

added check and abort when no test points are specified
AlanFord
committed
altered call to openfixture.scad to properly pass the pcb support border size
AlanFord
committed

Commits on Mar 2, 2018

added back cutout to the head top plate to resolve top-back interferences
AlanFord
committed