Refactoring, consisting of
- remove unused method `isAuxiliaryLanguage` and `FileCountList`
in order to reduce public API surfaces (go/java)
- add GoDoc to public APIs
- ci: java profile use latest go src
It also now mimics https://docs.travis-ci.com/user/languages/go/#go-import-path
for non-go build image, as code relies on internal imports.
TEST PLAN:
- make test
