1377 - Blacklist dependencies from SCM tracking

Git excludes dependencies from commit. 
Mercurial just shows a warning because it doesn't support excludes on commits. Just hgignore
I'm not sure this is a good idea. For example, What if you already have modules/concat/ but it's not it the exclude file? In that case it would't be excluded if the Ignore function is at the end of `ensure_repo()`