Fixed a MANIFEST issue

MANIFEST.in

@@ -4,6 +4,8 @@ recursive-include examples *
 recursive-include docs *
 recursive-exclude docs *.pyc
 recursive-exclude docs *.pyo
+recursive-exclude tests *.pyc
+recursive-exclude tests *.pyo
 recursive-exclude examples *.pyc
 recursive-exclude examples *.pyo
 prune docs/_build