Minor typo (release docs for 0.13.0)

[aldanor]

Replace serach with search in https://github.com/pydata/pandas/blob/master/doc/source/v0.13.0.txt#L161.

[jorisvandenbossche]

If you want, you can change it yourself. Push the edit button in your link, edit the line, and then automatically a PR will be created.

[aldanor]

Thanks Joris; submitted #5547.