only auto-clean whitespaces on save in modes specifically set to do so

custom-variables.el

@@ -44,6 +44,7 @@
  '(tool-bar-mode nil)
  '(undo-tree-mode-lighter "")
  '(visual-line-mode nil t)
+ '(whitespace-action nil)
  '(winner-mode t nil (winner))
  '(yas/global-mode t nil (yasnippet))
  '(yas/snippet-dirs (quote ("~/.emacs.d/snippets/custom" "~/.emacs.d/snippets/stock" "~/.emacs.d/el-get/yasnippet/snippets")) nil (yasnippet))

languages/cucumber.el

@@ -1 +1,5 @@
 (add-to-list 'auto-mode-alist '("\\.feature" . feature-mode))
+
+(add-hook 'feature-mod-hook
+          (lambda ()
+            (setq whitespace-action (quote (auto-cleanup)))))