umlauts in dataframe cannot be displayed in ipython notebook
When I put this into a ipython notebook cell, an exception is thrown. 

``` python
import pandas
data2 = [u"test", u"ß", u"ä", u"á"]
df2 = pandas.DataFrame({"a":data2})
print(df2["a"][1])
df2
```

```
ß
---------------------------------------------------------------------------
UnicodeDecodeError                        Traceback (most recent call last)
<ipython-input-5-0bb7d6f7d515> in <module>()
      2 df2 = pandas.DataFrame({"a":data2})
      3 print(df2["a"][1])
----> 4 df2

C:\portabel\Python27\lib\site-packages\IPython\core\displayhook.pyc in __call__(self, result)
    244             self.update_user_ns(result)
    245             self.log_output(format_dict)
--> 246             self.finish_displayhook()
    247 
    248     def flush(self):

C:\portabel\Python27\lib\site-packages\IPython\zmq\displayhook.pyc in finish_displayhook(self)
     59         sys.stdout.flush()
     60         sys.stderr.flush()
---> 61         self.session.send(self.pub_socket, self.msg, ident=self.topic)
     62         self.msg = None
     63 

C:\portabel\Python27\lib\site-packages\IPython\zmq\session.pyc in send(self, stream, msg_or_type, content, parent, ident, buffers, track, header, metadata)
    576 
    577         buffers = [] if buffers is None else buffers
--> 578         to_send = self.serialize(msg, ident)
    579         to_send.extend(buffers)
    580         longest = max([ len(s) for s in to_send ])

C:\portabel\Python27\lib\site-packages\IPython\zmq\session.pyc in serialize(self, msg, ident)
    484             content = self.none
    485         elif isinstance(content, dict):
--> 486             content = self.pack(content)
    487         elif isinstance(content, bytes):
    488             # content is already packed, as in a relayed message

C:\portabel\Python27\lib\site-packages\IPython\zmq\session.pyc in <lambda>(obj)
     78 _version_info_list = list(IPython.version_info)
     79 # ISO8601-ify datetime objects
---> 80 json_packer = lambda obj: jsonapi.dumps(obj, default=date_default)
     81 json_unpacker = lambda s: extract_dates(jsonapi.loads(s))
     82 

C:\portabel\Python27\lib\site-packages\zmq\utils\jsonapi.pyc in dumps(o, **kwargs)
     70         kwargs['separators'] = (',', ':')
     71 
---> 72     return _squash_unicode(jsonmod.dumps(o, **kwargs))
     73 
     74 def loads(s, **kwargs):

C:\portabel\Python27\lib\site-packages\simplejson\__init__.pyc in dumps(obj, skipkeys, ensure_ascii, check_circular, allow_nan, cls, indent, separators, encoding, default, use_decimal, namedtuple_as_object, tuple_as_array, bigint_as_string, sort_keys, item_sort_key, **kw)
    332         sort_keys=sort_keys,
    333         item_sort_key=item_sort_key,
--> 334         **kw).encode(obj)
    335 
    336 

C:\portabel\Python27\lib\site-packages\simplejson\encoder.pyc in encode(self, o)
    235         # exceptions aren't as detailed.  The list call should be roughly
    236         # equivalent to the PySequence_Fast that ''.join() would do.
--> 237         chunks = self.iterencode(o, _one_shot=True)
    238         if not isinstance(chunks, (list, tuple)):
    239             chunks = list(chunks)

C:\portabel\Python27\lib\site-packages\simplejson\encoder.pyc in iterencode(self, o, _one_shot)
    309                 Decimal=Decimal)
    310         try:
--> 311             return _iterencode(o, 0)
    312         finally:
    313             key_memo.clear()

UnicodeDecodeError: 'utf8' codec can't decode byte 0xdf in position 22: invalid continuation byte

```

This also happens when I have umlauts in csv files and specify an encoding:

```
df3 = pandas.read_csv("file_with_unlauts.csv", encoding="iso-8859-15")
print(df3.head(10)["name"][8]) # prints the right chars
df3.head(10) # throws the above error
```
