Restore git-gutter:diff-option

Because a few people use this option.

See also
  https://github.com/search?q=git-gutter%3Adiff-option&ref=cmdform&type=Code
Update support version
Use custom-set-variables instead of setq

And remove needless information
Remove focus-in-hook

It should not be default update hooks, because it cannot be used
in terminal-mode.

And I typoed :(
Add customize variables about updating diff info