jmrodri and Erik Nelson add prune rules (#8)
bf1c2b5 Jul 13, 2018
add prune rules (#8)
unused-packages will remove anything that we don't directly import which
could make library development annoying if things are missing.

non-go will remove all the non-go files like README, Makefile, etc.

go-tests removes test files which aren't required
bf1c2b5