Move Scroller.init() up the handler stack.

Move scroller initialisation so that its key handlers are above insert
mode in the handler stack.  This ensures that the scroller sees keyup
events if we enter insert mode while continuous scrolling.

Fixes #1526.

content_scripts/vimium_frontend.coffee

@@ -133,15 +133,14 @@ window.initializeModes = ->
         keypress: (event) => onKeypress.call @, event
         keyup: (event) => onKeyup.call @, event
 
-      Scroller.init settings
-
   # Install the permanent modes.  The permanently-installed insert mode tracks focus/blur events, and
   # activates/deactivates itself accordingly.
   new BadgeMode
   new NormalMode
   new PassKeysMode
   new InsertMode permanent: true
   new GrabBackFocus
+  Scroller.init settings
 
 #
 # Complete initialization work that sould be done prior to DOMReady.