Delete the local test variable to prevent a test-run error.

Currently, `nosetests --with-doctest` (which includes mustache spec
tests) is at the following:

----------------------------------------------------------------------
Ran 234 tests in 0.407s

FAILED (errors=3, failures=27)

All errors/failures are with spec tests.

tests/test_spec.py

@@ -61,6 +61,8 @@ for spec in specs:
     for test in yaml.load(open(spec))['tests']:
         test = buildTest(test, file_name)
         setattr(MustacheSpec, test.__name__, test)
+        # Prevent this variable from being interpreted as another test.
+        del(test)
 
 if __name__ == '__main__':
     unittest.main()