setup.py: dependency multiprocessing==2.6.2.1 -> multiprocessing

setup.py

@@ -135,7 +135,7 @@ install_requires.extend([
 
 py_version = sys.version_info
 if sys.version_info < (2, 6):
-    install_requires.append("multiprocessing==2.6.2.1")
+    install_requires.append("multiprocessing")
 if sys.version_info < (2, 5):
     install_requires.append("uuid")