Extra empty row when saving to CSV with MultiIndex columns

[jluttine]

If using MultiIndex as columns, saving to CSV adds an extra line with no data between the column headers and the data. I couldn't find information that this is something that should happen so it was unexpected to me.

Code Sample, a copy-pastable example if possible

In IPython:

import pandas as pd
pd.DataFrame({('a','b'): [1, 2], ('c','d'): [3, 4]}).to_csv('temp.csv', index=False)
cat temp.csv

Outputs:

a,c
b,d
,
1,3
2,4

Expected Output

I expected not to have an empty row between column names and the data:

a,c
b,d
1,3
2,4

output of pd.show_versions()

INSTALLED VERSIONS
------------------
commit: None
python: 3.5.1.final.0
python-bits: 64
OS: Linux
OS-release: 4.5.2-gnu-1
machine: x86_64
processor: 
byteorder: little
LC_ALL: None
LANG: en_DK.UTF-8

pandas: 0.18.0
nose: 1.3.7
pip: 8.1.1
setuptools: 20.10.1
Cython: 0.24
numpy: 1.11.0
scipy: 0.17.0
statsmodels: None
xarray: None
IPython: 4.2.0
sphinx: 1.4
patsy: None
dateutil: 2.5.3
pytz: 2016.4
blosc: None
bottleneck: None
tables: 3.2.2
numexpr: 2.5.2
matplotlib: 1.5.1
openpyxl: None
xlrd: 0.9.4
xlwt: None
xlsxwriter: None
lxml: None
bs4: 4.4.1
html5lib: None
httplib2: 0.9.2
apiclient: 1.5.0
sqlalchemy: 1.0.12
pymysql: None
psycopg2: 2.6.1 (dt dec pq3 ext lo64)
jinja2: 2.8
boto: None

[jluttine]

Oh, duplicate of #6618 I think.