Add README.

README.md

+# SimSo
+
+SimSo is a scheduling simulator designed for the study of real-time scheduling algorithms.
+
+- Project website: http://www.laas.fr/~mcheramy/simso/
+- Documentation: http://homepages.laas.fr/mcheramy/simso/doc/
+
+You can find its graphical user interface here: https://github.com/MaximeCheramy/simso-gui
+
+This is a free software available under the CeCILL license (GPL compatible).