Upgrade firefox-esr-cn to 31.0

Casks/firefox-esr-cn.rb

@@ -1,7 +1,7 @@
 class FirefoxEsrCn < Cask
-  url 'https://download.mozilla.org/?product=firefox-24.6.0esr&os=osx&lang=zh-CN'
+  url 'https://download.mozilla.org/?product=firefox-31.0esr&os=osx&lang=zh-CN'
   homepage 'http://www.mozilla.org/en-US/firefox/organizations/faq/'
-  version '24.6.0'
+  version '31.0'
-  sha256 '711b536b48c6e5a61480604e3b3555560d12638781a77f5f30b2e9cd6788b1db'
+  sha256 'b1a8bb972f94052813be5b78e8e8aa56357f87a953bd0cfb1686822494ea3488'
   link 'Firefox.app'
 end