Remove redundant Python 2.4 code

tweepy/cache.py

@@ -6,6 +6,7 @@ from __future__ import print_function
 
 import time
 import datetime
+import hashlib
 import threading
 import os
 import logging
@@ -15,12 +16,6 @@ try:
 except ImportError:
     import pickle
 
-try:
-    import hashlib
-except ImportError:
-    # python 2.4
-    import md5 as hashlib
-
 try:
     import fcntl
 except ImportError: