Remove bash-git-prompt as submodule

I am changing it to subtree.
Squashed '.bash/' content from commit 6ce9e75

git-subtree-dir: .bash
git-subtree-split: 6ce9e757d240d042dc839f542a5411aa6eae9506
Merge commit '220f9ff64f3880f56f0d012750ce6a4278007cae' as '.bash'