introduce minimal update interval(Default is 1 second)
Add explanation of updating gutter threshold
Fix defcustom type
Merge branch 'improve_slow'
Bump up version and update Changes

Fix for #26 issue
Use 'file-remote-p' instead of 'tramp-connectable-p'(#27)

Because 'tramp-connectable-p' is implemented at Emacs 23.3.
Fix test for 12c618a
Bump up version and update Changes
Update document
Fix problem of narrow-to-region(#28)

Reported by ZaneA
Bump up version and update Changes