Remove bootstrap submodule and .gitmodules (changing git module to subtree).
Squashed 'bootstrap/' content from commit 866ffc4

git-subtree-dir: bootstrap
git-subtree-split: 866ffc4f37def3d505a10a161720dc0ef9420dea
Merge commit 'c9cd1817fd7b49480b7aaaa4bb6f9e96778922ab' as 'bootstrap'