pandas.tests.test_panel4d.TestPanel4d.test_sum fails in 0.17.0
```
% nosetests -v pandas.tests.test_panel4d:TestPanel4d.test_sum
test_sum (pandas.tests.test_panel4d.TestPanel4d) ... FAIL

======================================================================
FAIL: test_sum (pandas.tests.test_panel4d.TestPanel4d)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/pandas/tests/test_panel4d.py", line 49, in test_sum
    self._check_stat_op('sum', np.sum)
  File "/usr/local/lib/python2.7/site-packages/pandas/tests/test_panel4d.py", line 148, in _check_stat_op
    assert_panel_equal(result, obj.apply(skipna_wrapper, axis=i))
  File "/usr/local/lib/python2.7/site-packages/pandas/util/testing.py", line 1048, in assert_panelnd_equal
    assert_func(litem, ritem, check_less_precise=check_less_precise)
  File "/usr/local/lib/python2.7/site-packages/pandas/util/testing.py", line 1028, in assert_frame_equal
    obj='DataFrame.iloc[:, {0}]'.format(i))
  File "/usr/local/lib/python2.7/site-packages/pandas/util/testing.py", line 925, in assert_series_equal
    check_less_precise, obj='{0}'.format(obj))
  File "pandas/src/testing.pyx", line 58, in pandas._testing.assert_almost_equal (pandas/src/testing.c:3809)
  File "pandas/src/testing.pyx", line 147, in pandas._testing.assert_almost_equal (pandas/src/testing.c:2685)
  File "/usr/local/lib/python2.7/site-packages/pandas/util/testing.py", line 798, in raise_assert_detail
    raise AssertionError(msg)
AssertionError: DataFrame.iloc[:, 1] are different

DataFrame.iloc[:, 1] values are different (12.5 %)
[left]:  [0.0, 1.11252805895, -3.44337874224, 1.77230240341, -1.27472712412, -0.953662849233, -0.819950380871, 3.3111686889]
[right]: [nan, 1.11252805895, -3.44337874224, 1.77230240341, -1.27472712412, -0.953662849233, -0.819950380871, 3.3111686889]

----------------------------------------------------------------------
Ran 1 test in 0.169s

FAILED (failures=1)
```

```
$ python2.7 -m pandas.util.print_versions

INSTALLED VERSIONS
------------------
commit: None
python: 2.7.10.final.0
python-bits: 64
OS: FreeBSD
OS-release: 10.1-STABLE
machine: amd64
processor: amd64
byteorder: little
LC_ALL: None
LANG: None

pandas: 0.17.0
nose: 1.3.7
pip: None
setuptools: 17.0
Cython: 0.23.4
numpy: 1.10.0
scipy: 0.16.0
statsmodels: None
IPython: 3.2.2
sphinx: None
patsy: None
dateutil: 2.3
pytz: 2015.7
blosc: None
bottleneck: 0.8.0
tables: 3.2.0
numexpr: 2.4.4
matplotlib: 1.4.3
openpyxl: 2.2.6
xlrd: 0.9.3
xlwt: 0.7.5
xlsxwriter: None
lxml: 3.4.1
bs4: 4.3.2
html5lib: 0.9999999
httplib2: None
apiclient: None
sqlalchemy: 0.7.10
pymysql: None
psycopg2: None
```
