Implement object specificity for dependent attribute declarations. [Closes #53]

@@ -80,8 +80,16 @@ class Rivets.Binding
       @sync() if Rivets.config.preloadData
 
     if @options.dependencies?.length
-      for keypath in @options.dependencies
-        Rivets.config.adapter.subscribe @model, keypath, @sync
+      for dependency in @options.dependencies
+        if /^\./.test dependency
+          model = @model
+          keypath = dependency.substr 1
+        else
+          dependency = dependency.split '.'
+          model = @view.models[dependency.shift()]
+          keypath = dependency.join '.'
+
+        Rivets.config.adapter.subscribe model, keypath, @sync
 
     if @isBidirectional()
       bindEvent @el, 'change', @publish