BUG: int64 overflow/wrap around with sum()
#### Code Sample, a copy-pastable example if possible

```python
In [1]: import pandas as pd

In [2]: s = pd.Series([2**31])

In [3]: print(s.dtype, s.sum())
(dtype('int64'), -2147483648)

In [4]: pd.Series([2**31 - 1, 1]).sum()
Out[4]: -2147483648

In [5]: pd.Series([2**31 - 1, 1]).astype('int32').sum()
Out[5]: 2147483648
```


#### Problem description

negative values in [3] and [4]

#### Expected Output

see [5]

#### Output of ``pd.show_versions()``

<details>

```python
In [6]: pd.show_versions()

INSTALLED VERSIONS
------------------
commit: None
python: 2.7.13.final.0
python-bits: 64
OS: Windows
OS-release: 7
machine: AMD64
processor: Intel64 Family 6 Model 42 Stepping 7, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.19.2
nose: 1.3.7
pip: 9.0.1
setuptools: 34.2.0
Cython: None
numpy: 1.12.0
scipy: 0.19.0rc1
statsmodels: 0.8.0
xarray: None
IPython: 5.2.2
sphinx: 1.5.2
patsy: None
dateutil: 2.6.0
pytz: 2016.10
blosc: None
bottleneck: 1.2.0
tables: None
numexpr: 2.6.2
matplotlib: 1.5.3
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: 4.5.3
html5lib: 0.999999999
httplib2: 0.10.3
apiclient: 1.6.2
sqlalchemy: 1.1.5
pymysql: None
psycopg2: 2.6.2 (dt dec pq3 ext lo64)
jinja2: 2.9.5
boto: None
pandas_datareader: None
```
</details>
