to_clipboard does not use the default options
#### Code Sample, a copy-pastable example if possible

```python
#This does not work as expected

print Final.corr().to_clipboard()

#But this works, even though it is the default option

print Final.corr().to_clipboard(sep='\t')
```
#### Problem description
I was working in this code for over a year without a single problem. Yesterday I had to format my PC and reinstall everything again. I found that, when trying to paste to Excel from clipboard, it does not longer format it correctly.

I don't think it is Canopy since I installed the same version that I've been using this past few months. I think that the last working version of Pandas that I used was 0.22.x. 

Pandas version 0.23.1-1

#### Expected Output
Excel compatible format
#### Output of ``pd.show_versions()``
<details>
[paste the output of ``pd.show_versions()`` here below this line]
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 60 Stepping 3, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.23.1
pytest: None
pip: 10.0.1
setuptools: 38.2.5
Cython: 0.25.2
numpy: 1.13.3
scipy: 1.0.0
pyarrow: None
xarray: None
IPython: 5.6.0
sphinx: None
patsy: 0.4.1
dateutil: 2.6.0
pytz: 2017.3
blosc: None
bottleneck: None
tables: 3.3.0
numexpr: 2.6.2
feather: None
matplotlib: 2.0.0
openpyxl: 2.4.1
xlrd: 1.0.0
xlwt: 1.2.0
xlsxwriter: None
lxml: 3.7.3
bs4: 4.6.0
html5lib: 0.9999999
sqlalchemy: 1.1.6
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: 0.6.0+34.gfeee4d7
</details>
