Added OpenSesame

OpenSesame is a graphical, open-source experiment builder for the
social sciences. It sports a modern and intuitive user interface that
allows you to build complex experiments with a minimum of effort. With
OpenSesame you can create a wide range of experiments. The plug-in
framework and Python scripting allow you to incorporate external
devices, such as eye trackers, response boxes, and parallel port
devices, into your experiment.