Fix import statement.

When importing pEp failed, and the program tries to import pEp again,
"NameError: name '_pEp' is not defined" was raised. This was caused by
"_pEp" not really been imported.

src/pEp/__init__.py

@@ -30,7 +30,7 @@ from ._pEp import *
 
 # import the native module into the current namespace because we also need to access the names beginning
 # with an underscore (of _pEp), but we dont want to import them into this module
-import pEp._pEp
+from . import _pEp
 
 # 3rd party imports
 from threading import Thread, Barrier