scatter_matrix mislabels axes with DataFrame index
python 2.7.3, pandas 0.8.0, matplotlib 1.1.0:

The example code at http://pandas.pydata.org/pandas-docs/stable/visualization.html#scatter-plot-matrix produces axis labels which are integers 0-9 instead of -4 to 4 or so (as determined by the data extent).  These appear to be taken from the DataFrame index, as can be seen by setting the index explicitly:

``` python
df = DataFrame(np.random.randn(6, 4), index=['x','y','z','p','d','q'], columns=['a', 'b', 'c', 'd'])
scatter_matrix(df, alpha=0.2, figsize=(8, 8), diagonal='kde')
```

produces http://imgur.com/oGFdM
