Don't perform the unbind + bind on the binder when updating the models. Allow a …

…custom update function on binders instead for them to handle updates. [#183]

@@ -137,10 +137,24 @@ class Rivets.Binding
 
   # Updates the binding's model from what is currently set on the view. Unbinds
   # the old model first and then re-binds with the new model.
-  update: =>
-    @unbind()
-    @model = if @key then @view.models[@key] else @view.models
-    @bind()
+  update: (models = {}) =>
+    if @key
+      if models[@key]
+        unless @options.bypass
+          @view.config.adapter.unsubscribe @model, @keypath, @sync
+
+        @model = models[@key]
+
+        if @options.bypass
+          @sync()
+        else
+          @view.config.adapter.subscribe @model, @keypath, @sync
+          @sync() if @view.config.preloadData
+
+        @binder.update?.call @, models
+    else
+      @sync()
+      @binder.update?.call @, models
 
 # Rivets.View
 # -----------
@@ -246,9 +260,8 @@ class Rivets.View
 
   # Updates the view's models along with any affected bindings.
   update: (models = {}) =>
-    for key, model of models
-      @models[key] = model
-      binding.update() for binding in @select (b) -> b.key is key
+    @models[key] = model for key, model of models
+    binding.update models for binding in @bindings
 
 # Rivets.Util
 # -----------