Use cl-lib instead of cl.el
Update dependency git-gutter version
Add Cask file for development
add .gitignore
Merge pull request #11 from syohex/next-release

Next release
Drop Emacs 23 support same as git-gutter

Because git-gutter drops Emacs 23 support.
And enable lexical-binding.
Bump up version and update Changes
Bump up version and update Changes