BUG: to_latex() output broken when the index has a name
Hey folks,

I posted this on [SO](https://stackoverflow.com/questions/31582114/groupby-to-latex-output-broken) and was asked to file a report here as well. 

I'm trying to export `pandas.DataFrame.describe()` to `LaTex` using the `to_latex()`-method. This works all fine as long as I don't apply the `groupby()`-method beforehand. With a grouped DataFrame, the first row has no values, even though its label is `count`. Note that the first row of a grouped dataframe is used to mark down the variable used for grouping in iPython notebook.

I'm using pandas 0.16.2, python 3.
Is this a bug or am I doing something wrong? 

Cheers,
Jakob

Here some examples:

Without `groupby`:

```
\begin{tabular}{lr}
\toprule
{} &    IS\_FEMALE \\
\midrule
count &  2267.000000 \\
mean  &     0.384649 \\
...
...
75\%   &     1.000000 \\
max   &     1.000000 \\
\bottomrule
\end{tabular}
```

[![enter image description here](http://i.stack.imgur.com/gK10V.png)](http://i.stack.imgur.com/gK10V.png)

With `groupby`:

```
\begin{tabular}{llr}
\toprule
  &       &    IS\_FEMALE \\
\midrule
0 & count &              \\     % <-- note missing value here
  & mean &  1134.000000 \\
  & std &     0.554674 \\
...
...
  & 75\% &     0.000000 \\
  & max &     0.000000 \\
\bottomrule
\end{tabular}
```

[![enter image description here](http://i.stack.imgur.com/lt9z9.png)](http://i.stack.imgur.com/lt9z9.png)

Output in the notebook:

[![enter image description here](http://i.stack.imgur.com/wT8Tp.png)](http://i.stack.imgur.com/wT8Tp.png)
