Add property to get morph key on token

spacy/tokens/token.pyx

@@ -169,6 +169,10 @@ cdef class Token:
         return (numpy.dot(self.vector, other.vector) /
                 (self.vector_norm * other.vector_norm))
 
+    property morph_key:
+        def __get__(self):
+            return self.c.morph
+
     property lex_id:
         """RETURNS (int): Sequential ID of the token's lexical type."""
         def __get__(self):