test_resample_median_bug_1688 fails locally
Travis passes, but locally:

```
FAIL: test_resample_median_bug_1688 (pandas.tseries.tests.test_resample.TestResample)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/alex/git/pandas/pandas/tseries/tests/test_resample.py", line 620, in test_resample_median_bug_1688
    tm.assert_frame_equal(result, exp)
  File "/home/alex/git/pandas/pandas/util/testing.py", line 303, in assert_frame_equal
    assert_isinstance(left, DataFrame)
  File "/home/alex/git/pandas/pandas/util/testing.py", line 170, in assert_isinstance
    type(obj), class_type_or_tuple))
AssertionError: Expected object to be of type <class 'pandas.core.series.Series'>, found <class 'pandas.core.frame.DataFrame'> instead
```
