DataFrame:iterrows() damages data integrity during interations
#### Code Sample, a copy-pastable example if possible

```python
# Your code here
 for _, row_arr in DataFrame.iterrows():
```
#### Problem description
For a DataFrame, there is one column that contains complex numbers

Once interating rows, all the values in each row become complex, where the real part is the original and the imagine part is given by 0*j

This is annoying, because one has to take care about this auto-conversion.

I would expect resolution on this, as data integrity shall not be polluted by iterations.

[this should explain **why** the current behaviour is a problem and why the expected output is a better solution.]

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#### Expected Output

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

<details>

[paste the output of ``pd.show_versions()`` here below this line]
INSTALLED VERSIONS
------------------
commit: None
python: 3.6.2.final.0
python-bits: 32
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 94 Stepping 3, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.23.4
pytest: None
pip: 18.0
setuptools: 40.5.0
Cython: None
numpy: 1.13.1
scipy: 1.1.0
pyarrow: None
xarray: None
IPython: None
sphinx: None
patsy: 0.4.1
dateutil: 2.6.1
pytz: 2017.2
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: 2.0.2
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
sqlalchemy: 1.2.9
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
</details>
