fix pair object in dict problem

jieba/posseg/__init__.py

@@ -84,6 +84,12 @@ class pair(object):
     def __lt__(self, other):
         return self.word < other.word
 
+    def __eq__(self, other):
+        return isinstance(other, pair) and self.word == other.word and self.flag == other.flag
+
+    def __hash__(self):
+        return hash(self.word)
+
     def encode(self, arg):
         return self.__unicode__().encode(arg)