version 0.13.1 appears as 0.12.0 in pip
I've installed the 0.13.1 version with pip, and it installed successfully.

But when checking in pip freeze I get:

```
pip freeze | grep pandas

pandas==0.12.0
```

It looks like the package is in the right version, ie:

```
In [11]: import pandas as pd; pd.__version__
Out[11]: '0.13.1'
```

and only pip thinks that the version is 0.12.0.

It is extremely annoying since I got pandas in a requirements file with the specific version, and every time I install the requirements, pandas is installed all over again
