Revert "Use fancy "-Z2" flag create integers with leading zeroes inside prompt."

This reverts commit 3e4901f3fb4aa1c4bf3aadc1b5ec6b4cbe1381e7.
Add number of unmerged files to Git prompt.
Use better symbols for Git status on dumb terminals.
Don't install the .gitsubmodules file.
Add git-wip, a more persistent alternative to git stash.

git-wip commits the current working tree to the current branch in a
commit named "wip!". A subsequent call to git-wip resets that commit.
Make git-quick-rebase a script, not an alias.

Since the alias already depended on a script, why not just do all the
work in the script.