Make sure all dependency observers get unbinded when calling Rivets.Binding::unbind().

@@ -64,13 +64,15 @@ class Rivets.Binding
         @set Rivets.config.adapter.read @model, @keypath
 
     if @options.dependencies?.length
-      for keypath in @options.dependencies
-        Rivets.config.adapter.subscribe @model, keypath, (stub) =>
+      @reset = (value) =>
         @set if @options.bypass
           @model[@keypath]
         else
           Rivets.config.adapter.read @model, @keypath
         
+      for keypath in @options.dependencies
+        Rivets.config.adapter.subscribe @model, keypath, @reset
+
     if @type in @bidirectionals
       bindEvent @el, 'change', @publish
 
@@ -83,6 +85,10 @@ class Rivets.Binding
   unbind: =>
     Rivets.config.adapter.unsubscribe @model, @keypath, @set
 
+    if @options.dependencies?.length
+      for keypath in @options.dependencies
+        Rivets.config.adapter.unsubscribe @model, keypath, @reset
+
     if @type in @bidirectionals
       @el.removeEventListener 'change', @publish