Add link to git-subtree
Squashed 'bundle/tagbar/' changes from dec1f84..ec0eb88

ec0eb88 Recognize racket as scheme, closes #134

git-subtree-dir: bundle/tagbar
git-subtree-split: ec0eb883dcce5ba3885b816e6a83992f8b56350c
Merge commit 'b67b660da9d76fc7d0827c4f0f9d9f6a4b92851c'
Update README to remove submodule instructions