Create test suite

[abetusk]

Create some sort of test suite so we're reasonably confident it's parsing and creating GCode files that match with the source Gerber files.

The first step is to parse all Gerber files in the tests directory as correctly as possible by visual inspection with the .png files provided or by running it through a Gerber rendering program and comparing results. In the future adding some automated scripts to at least make sure there are no parse errors would be helpful.