Fixed caching issues

Fixed exception raised during cache reading

Switched cache hashing to hashlib

In python 3.3 the hash function is returning different hashes during
different executions of the application.

jedi/parsing_representation.py

@@ -560,7 +560,7 @@ class Flow(Scope):
     @parent.setter
     def parent(self, value):
         self._parent = value
-        if self.next:
+        if hasattr(self, "next") and self.next:
             self.next.parent = value
 
     def get_code(self, first_indent=False, indention='    '):