Save last scrollposition and scroll back when leaving ZEN mode

app/assets/javascripts/zen_mode.js.coffee

@@ -4,10 +4,16 @@ class @ZenMode
   constructor: ->
     @active_zen_area = null
     @active_checkbox = null
+    @scroll_position = 0
+
+    $(window).scroll =>
+      if not @active_checkbox
+        @scroll_position = window.pageYOffset
 
     $('body').on 'change', '.zennable input[type=checkbox]', (e) =>
       checkbox = e.currentTarget
       if checkbox.checked
+        # Disable other keyboard shortcuts in ZEN mode
         Mousetrap.pause()
         @udpateActiveZenArea(checkbox)
       else
@@ -34,6 +40,7 @@ class @ZenMode
       @active_zen_area = null
       @active_checkbox = null
       window.location.hash = ''
+      window.scrollTo(window.pageXOffset, @scroll_position)
 
   checkboxFromLocationHash: (e) ->
     id = $.trim(window.location.hash.replace('#' + ZenMode.fullscreen_prefix, ''))