Unicode, unique, and ndarrays
More unicode fun. I seem to recall seeing this before, but I can't find anything about it. Is this numpy, what pandas hands off to numpy, or user error?

``` python
df = pandas.DataFrame([u"\xe9"])
df[0].unique()
<snip>
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/numpy/core/numeric.py", line 1409, in array_repr
    ', ', "array(")
  File "/usr/local/lib/python2.7/dist-packages/numpy/core/arrayprint.py", line 445, in array2string
    separator, prefix, formatter=formatter)
  File "/usr/local/lib/python2.7/dist-packages/numpy/core/arrayprint.py", line 320, in _array2string
    _summaryEdgeItems, summary_insert)[:-1]
  File "/usr/local/lib/python2.7/dist-packages/numpy/core/arrayprint.py", line 491, in _formatArray
    word = format_function(a[-1])
UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' in position 0: ordinal not in range(128)
```

```
pandas.version.version
'0.9.0rc1'

np.version.full_version
'1.8.0.dev-578a419'
```
