Optimize setting overlays

- reduce 'save-excursion' as possible
Merge branch 'master' into optimize-view
Remove git-gutter:view-region and inlining
Merge pull request #55 from syohex/optimize-view

Optimize view
Reduce needless function calling

It is enough to call 'git-gutter:linum-padding' only once.
Bump up version and update Changes
Merge remote-tracking branch 'refs/remotes/upstream/master'