Correct perf test for series rolling (#597)

* parallel and add mask for methods: capitalize, casefold, swapcase, title

* correct master

* add empty line

* fix apply

* fix

Author: Rubtsowa

sdc/tests/tests_perf/test_perf_series_rolling.py

@@ -84,7 +84,7 @@ def _test_case(self, pyfunc, name, total_data_length, data_num=1,
 
 
 cases = [
-    TC(name='apply', size=[10 ** 7], params='func=lambda x: numpy.nan if len(x) == 0 else x.mean()', skip=True),
+    TC(name='apply', size=[10 ** 7], params='func=lambda x: np.nan if len(x) == 0 else x.mean()'),
     TC(name='corr', size=[10 ** 7]),
     TC(name='count', size=[10 ** 7]),
     TC(name='cov', size=[10 ** 7]),