Add colortable utility

autoload/lightline/colortable.vim

@@ -0,0 +1,17 @@
+function! s:load()
+  let rgbfile = $VIMRUNTIME . '/rgb.txt'
+  let table = {}
+  if filereadable(rgbfile)
+    for _ in map(filter(readfile(rgbfile), 'v:val !~ "^!"'), 'matchlist(v:val, "^\\s*\\(\\d\\+\\)\\s\\+\\(\\d\\+\\)\\s\\+\\(\\d\\+\\)\\s\\+\\(.*\\)")[1:4]')
+      let table[tolower(_[3])] = _[0:2]
+    endfor
+  endif
+  return table
+endfunction
+
+let s:table = s:load()
+
+function! lightline#colortable#name_to_rgb(name)
+  let name = tolower(a:name)
+  return has_key(s:table, name) ? s:table[name] : []
+endfunction