Improved the performance of bindEvent, unbindEvent, getInputValue on Rivets.Util.

 # Rivets.Util
 # -----------
 
-# Houses common utility functions used internally by Rivets.js.
-Rivets.Util =
-  # Create a single DOM event binding.
-  bindEvent: (el, event, handler) ->
-    if window.jQuery?
-      el = jQuery el
-      if el.on? then el.on event, handler else el.bind event, handler
-    else if window.addEventListener?
+if 'jQuery' of window
+  [bindMethod, unbindMethod] = if 'on' of jQuery then ['on', 'off'] else ['bind', 'unbind']
+  
+  Rivets.Util =
+    bindEvent: (el, event, handler) -> jQuery(el)[bindMethod] event, handler
+    unbindEvent: (el, event, handler) -> jQuery(el)[unbindMethod] event, handler
+    getInputValue: (el) ->
+      $el = jQuery el
+
+      if $el.attr('type') is 'checkbox' then $el.is ':checked'
+      else do $el.val
+else
+  Rivets.Util =
+    bindEvent: do ->
+      if 'addEventListener' of window then return (el, event, handler) ->
         el.addEventListener event, handler, false
-    else
-      event = 'on' + event
-      el.attachEvent event, handler
 
-  # Remove a single DOM event binding.
-  unbindEvent: (el, event, handler) ->
-    if window.jQuery?
-      el = jQuery el
-      if el.off? then el.off event, handler else el.unbind event, handler
-    else if window.removeEventListener?
+      (el, event, handler) -> el.attachEvent 'on' + event, handler
+    unbindEvent: do ->
+      if 'removeEventListener' of window then return (el, event, handler) ->
         el.removeEventListener event, handler, false
-    else
-      event = 'on' + event
-      el.detachEvent  event, handler
       
-  # Get the current value of an input node.
+      (el, event, handler) -> el.detachEvent 'on' + event, handler
     getInputValue: (el) ->
-    if window.jQuery?
-      el = jQuery el
-
-      switch el[0].type
-        when 'checkbox' then el.is ':checked'
-        else el.val()
-    else
-      switch el.type
-        when 'checkbox' then el.checked
-        when 'select-multiple' then o.value for o in el when o.selected
+      if el.type is 'checkbox' then el.checked
+      else if el.type is 'select-multiple' then o.value for o in el when o.selected
       else el.value
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