Process the declaration into a binding if the key is null or if a model exists a…

…t the specific key. [#172]

@@ -208,7 +208,7 @@ class Rivets.View
               splitPath.shift()
             keypath = splitPath.join '.'
 
-            if @models[key]?
+            if not key or @models[key]?
               if dependencies = context.shift()
                 options.dependencies = dependencies.split /\s+/