Quick fix for i18n

Just use the english locale for now. Load locale data from the
filesystem in the main process and pass it to the renderer preload
script via ipc. Note that we need the locale data to be available by the
time view scripts are loaded.

// FREEBIE

background.html

@@ -731,6 +731,7 @@
   <script type='text/javascript' src='js/conversation_controller.js'></script>
   <script type='text/javascript' src='js/panel_controller.js'></script>
   <script type='text/javascript' src='js/emoji_util.js'></script>
+  <script type='text/javascript' src='js/i18n.js'></script>
 
   <script type='text/javascript' src='js/views/whisper_view.js'></script>
   <script type='text/javascript' src='js/views/last_seen_indicator_view.js'></script>