ipython: bump to 0.13.1

IPython 0.13.1: minor bugfix release for 0.13, on October 20, 2012. This
release includes 41 Pull Requests and closing 21 Issues backported from
0.14-dev, including significant fixes for ipcluster and Python 3.3
compatibility.
Merge pull request #414 from bjornfor/ipython-version-bump

ipython: bump to 0.13.1