Dual license these dotfiles under MIT/GPL

As requested by @lathan. Closes #205.
.osx: Fix `ShowPathBar` typo

Closes #204.
.bash_profile: Try to grunt more quietly

Ref. #209.
.functions: Add `gitio`

Closes #210.
.osx: Don’t automatically rearrange Spaces

Closes #213.
.gitconfig: Tweak `l` alias
Update to Bash v4.2.45
.osx: Update the GitHub fork link

Closes #221.
Remove GPL license

The MIT license is GPL-compatible anyway, as per @sindresorhus. Ref. https://github.com/mathiasbynens/dotfiles/commit/a89e2f2d226de274c998b0b8de5fd4af2e0b444f#commitcomment-3485954.
bootstrap.sh: Avoid `source` if there are no changes

Closes #220.
Merge in upstream