BUG: read_clipboard fails on Windows since pandas 0.12
Since I updated pandas from version 0.11 to 0.12, read_clipboard fails:

```
import pandas as pd    
df = pd.read_clipboard()
```

Results in:

```
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-2-6dead334eb54> in <module>()
----> 1 df = pd.read_clipboard()

C:\Python33\lib\site-packages\pandas\io\clipboard.py in read_clipboard(**kwargs)
     16     from pandas.io.parsers import read_table
     17     text = clipboard_get()
---> 18     return read_table(StringIO(text), **kwargs)
     19 
     20 

TypeError: initial_value must be str or None, not bytes
```

What I did was:
- Open a csv file in Excel 2010
- Copy a range of cells, including headers
- Perform read_clipboard in iPython Qt console as described in above code block

After downgrading to 0.11, this procedure worked fine again.

OS: Win7, 64bit
Python: v3.3.2 32-bit
Pandas: 0.12.0
Numpy: 1.7.1
