add --passthrough and --ignore

-- passthrough will tell harmonizer to not harmonize certain files
-- ignore will tell harmonizer to not consider certain files
-- both accept globs
npmignore
made extend/spread into strings (thank the lords for templates)

 - previously it used to do function.toString(), which is fine and dandy, but istanbul writes to functions, so the toStringed version had istanbul crap in it, when running test coverage.
npm test, istanbul
add main index file for code coverage, moved rest to test/transform