tools.tests.test_tile:TestCut.test_inf_handling generates error on FreeBSD
```
$ nosetests -v pandas.tools.tests.test_tile:TestCut.test_inf_handling
test_inf_handling (pandas.tools.tests.test_tile.TestCut) ... ERROR

======================================================================
ERROR: test_inf_handling (pandas.tools.tests.test_tile.TestCut)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/obrienjw/src/github/pandas/pandas/tools/tests/test_tile.py", line 121, in test_inf_handling
    result = cut(data, [-np.inf, 2, 4, np.inf])
  File "/home/obrienjw/src/github/pandas/pandas/tools/tile.py", line 103, in cut
    include_lowest=include_lowest)
  File "/home/obrienjw/src/github/pandas/pandas/tools/tile.py", line 169, in _bins_to_cuts
    include_lowest=include_lowest)
  File "/home/obrienjw/src/github/pandas/pandas/tools/tile.py", line 205, in _format_levels
    fa, fb = fmt(a), fmt(b)
  File "/home/obrienjw/src/github/pandas/pandas/tools/tile.py", line 201, in <lambda>
    fmt = lambda v: _format_label(v, precision=prec)
  File "/home/obrienjw/src/github/pandas/pandas/tools/tile.py", line 235, in _format_label
    return '%d' % (-whole - 1)
TypeError: %d format: a number is required, not numpy.float64

----------------------------------------------------------------------
Ran 1 test in 0.002s

FAILED (errors=1)
```

My environment:

```
$ git describe
v0.12.0-1110-gd250d64
$ ci/print_versions.py

INSTALLED VERSIONS
------------------
Python: 2.7.5.final.0
OS: FreeBSD 9.2-PRERELEASE FreeBSD 9.2-PRERELEASE #0 r254955: Tue Aug 27 11:01:00 EDT 2013     root@drivel.saltant.net:/usr/obj/usr/src/sys/NARB amd64
byteorder: little
LC_ALL: None
LANG: None

pandas: Not installed
Cython: 0.19.1
Numpy: 1.7.0
Scipy: 0.12.1
statsmodels: Not installed
    patsy: Not installed
scikits.timeseries: Not installed
dateutil: 2.1
pytz: 2013.8
bottleneck: Not installed
PyTables: Not Installed
    numexpr: 2.2.2
matplotlib: 1.2.0
openpyxl: Not installed
xlrd: Not installed
xlwt: Not installed
xlsxwriter: Not installed
sqlalchemy: Not installed
lxml: Not installed
bs4: Not installed
html5lib: Not installed
bigquery: Not installed
apiclient: Not installed
```
