Add match id to json template.
Fix crash bug when --show is turned on.

Found thanks to trying to raise test coverage! :D Turns out I was trying to draw match_rects from a match out of range (used match_count instead of match_count - 1)
Don't compile gpio stuff for non RPI at all.

This just lowers the test coverage! :p
Enable showing images in tests as well.

This found a crash bug and raises the code coverage. Not sure if this works properly on Travis however...