read_csv parses  header incorrectly
```python
from io import StringIO
csv = r"""Physical\Flows.Solve,9,1,4,0,0,0,0,0,0
1,2,3,4,5,6,7,8,9,10
"""
csv = StringIO(csv)
pd.read_csv(csv, engine='python')
```
Results in: 
![image](https://user-images.githubusercontent.com/881019/35954774-5cd523e6-0cd7-11e8-80b2-9a15efed3a73.png)

#### Problem description
As can be seen the integer zeros have been cast to non-zero floats!


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

<details>

```
INSTALLED VERSIONS
------------------
commit: None
python: 3.6.4.final.0
python-bits: 64
OS: Windows
OS-release: 7
machine: AMD64
processor: Intel64 Family 6 Model 62 Stepping 4, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.22.0
pytest: 3.3.0
pip: 9.0.1
setuptools: 38.4.0
Cython: 0.27.3
numpy: 1.13.3
scipy: 1.0.0
pyarrow: 0.8.0
xarray: 0.10.0
IPython: 6.2.1
sphinx: 1.6.7
patsy: 0.4.1
dateutil: 2.6.1
pytz: 2017.3
blosc: 1.5.1
bottleneck: 1.2.1
tables: 3.4.2
numexpr: 2.6.4
feather: None
matplotlib: 2.1.2
openpyxl: 2.5.0b1
xlrd: 1.1.0
xlwt: 1.3.0
xlsxwriter: 1.0.2
lxml: 4.1.1
bs4: 4.6.0
html5lib: 0.9999999
sqlalchemy: 1.1.13
pymysql: 0.8.0
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
```
</details>
