Add "corner" function
Something like [this](http://cran.r-project.org/web/packages/useful/useful.pdf).

I often have `DataFrame`s that have 4 - 5 `MultiIndex` levels on each axis and I can't get a visual idea about the structure unless I do something like

``` python
df.head().T.head().T
```

Of course, in the case that the indices are simple I can just slice the `ix` attribute, but for `MultiIndex`ed `DataFrame`s I can't do that.

I've written the following as as starter:

``` python
def corner(df, r=5, c=5):
    return df.head(r).T.head(c).T
```

Aside from being ugly, this code shouldn't have any issues. I'm not sure if the case of many-leveled `MultiIndex`es is very common, so feel free to close this if it doesn't seem that useful. I'd also like to know if there's another way to achieve this, if possible.
