Merge pull request #112 from jgeisler0303/simulator

Grbl Simulator. Oh yeah.
Fix sim makefile so it works on mac

These changes include a path separator fix and the removal of --gc-sections which causes ld failures, and is not needed on a pc.

This patch also changes how a compiler is selected.  The makefile will now select the system compiler , which should work fine
under mingw and linux.
Merge pull request #167 from tmpvar/simulator-mac

Fix sim makefile so it works on mac
Merge bug fixes from recent v0.8c push. Added readme for Grbl Sim.
implemented a mixture of Sonny's MATLAB and my previous grbl planner
ontop of the edge planner
examples run byte for byte identical old and new version
added counter for planner steps