Segmentation fault: 11 on nosetests
Nosetests results in the segmentation fault error:

```
$ nosetests pandas
................/Users/v/.virtual_envs/system/lib/python2.7/site-packages/pandas/core/index.py:910: RuntimeWarning: tp_compare didn't return -1 or -2 for exception
  result.sort()
................../Users/v/.virtual_envs/system/lib/python2.7/site-packages/numpy/core/fromnumeric.py:788: RuntimeWarning: tp_compare didn't return -1 or -2 for exception
  a.sort(axis, kind, order)
..................................................................................................................................................................................................................................F....................................S...S.....S..........................................SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS..................................................................................................................................................................................................................................................................................................................................................................S....................................................................................................................................S..........S......................................................................................................................................SSSS............................S................................................................SSSSSSSSSS......................SS.....................................................................................................................................................S...Segmentation fault: 11
```

It crashes on the following test:

```
...
test_binop_maybe_preserve_name (pandas.sparse.tests.test_sparse.TestSparseSeries) ... ok
test_combine_first (pandas.sparse.tests.test_sparse.TestSparseSeries) ... ok
test_combine_first_dt64 (pandas.sparse.tests.test_sparse.TestSparseSeries) ... ok
test_combine_first_name (pandas.sparse.tests.test_sparse.TestSparseSeries) ... Segmentation fault: 11
```

Operating system: OSX 10.9.1 Mavericks. Library versions:

```
>>> show_versions()

INSTALLED VERSIONS
------------------
Python: 2.7.6.final.0
OS: Darwin
Release: 13.0.0
Processor: i386
byteorder: little
LC_ALL: en_US.UTF-8
LANG: en_US.UTF-8

pandas: 0.13.0
Cython: 0.20
Numpy: 1.9.0.dev-783b96d
Scipy: 0.13.2
statsmodels: 0.5.0
    patsy: 0.2.1
scikits.timeseries: Not installed
dateutil: 2.1
pytz: 2013.9
bottleneck: 0.8.0
PyTables: 3.0.0
    numexpr: 2.2.2
matplotlib: 1.1.1
openpyxl: 1.8.2
xlrd: 0.9.2
xlwt: Not installed
xlsxwriter: Not installed
sqlalchemy: 0.9.1
lxml: 3.2.5
bs4: 4.3.2
html5lib: 0.999
bigquery: Not installed
apiclient: Not installed
```
