update signs on CursorHold or CursorHoldI

I added 2 new options that are disabled by default. Sign updating can
now be triggered after 'updatetime' miliseconds without keypresses in
either normal or insert mode:

For enabling:

let g:signify_cursorhold_normal = 1
let g:signify_cursorhold_insert = 1

README.md

@@ -76,6 +76,9 @@ For more info: `:h signify-options`
 
     let g:signify_enable_cvs = 1
 
+    let g:signify_cursorhold_normal = 1
+    let g:signify_cursorhold_insert = 1
+
 ## Author
 
 Marco Hinz `<mh.codebro@gmail.com>`

doc/signify.txt

@@ -141,6 +141,14 @@ The highlight groups to use with line highlighting.
 Enable CVS repo detection.
 
 
+    let g:signify_cursorhold_normal = 1
+    let g:signify_cursorhold_insert = 1
+
+Additionally trigger sign updates in normal or insert mode after 'updatetime'
+miliseconds without any keypresses. This fires only once between keypresses,
+thus not every 'updatetime' miliseconds.
+
+
 ==============================================================================
 4. Commands                                                 *signify-commands*
 4. Mappings                                                 *signify-mappings*

plugin/signify.vim

@@ -100,11 +100,17 @@ else
 endif
 
 "  Initial stuff  {{{1
-aug signify
-  au!
-  au ColorScheme * call s:colors_set()
-  au BufWritePost,BufEnter,FocusGained * call s:start(resolve(expand('<afile>:p')))
-aug END
+augroup signify
+  autocmd!
+  if exists('g:signify_cursorhold_normal') && (g:signify_cursorhold_normal == 1)
+    autocmd CursorHold * write | call s:start(resolve(expand('<afile>:p')))
+  endif
+  if exists('g:signify_cursorhold_insert') && (g:signify_cursorhold_insert == 1)
+    autocmd CursorHoldI * write | call s:start(resolve(expand('<afile>:p')))
+  endif
+  autocmd ColorScheme * call s:colors_set()
+  autocmd BufWritePost,BufEnter,FocusGained * call s:start(resolve(expand('<afile>:p')))
+augroup END
 
 com! -nargs=0 -bar SignifyToggle          call s:toggle_signify()
 com! -nargs=0 -bar SignifyToggleHighlight call s:toggle_line_highlighting()