Install `ZEO[test]` when testing.

`ZEO[test]` should be installed when testing, so that `zope.testing` is
installed.
Otherwise, an import error may be raised when running the test if
`zope.testing` has not been manually installed.

setup.py

@@ -401,7 +401,7 @@ setup(
                      'pytest',
                      'scipy',
                      'neoppod',     # lib/tests/test_zodb.py
-                     'ZEO',         # lib/tests/test_zodb.py
+                     'ZEO[test]',         # lib/tests/test_zodb.py
                     ],
     },