Add git submodule for handling test cases of .tim conversion and other things

[theeldestelder]

#11 needs to be compared to Vixen 3's output for the same input files to verify that it is doing things correctly. Keep these files separate from the main repository by including them as a git submodule.

[theeldestelder]

A repository has been created here: https://github.com/teslaworksumn/gallium-test-files. There just needs to be a PR to get this as a submodule of this repo