Update README.

README.md

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 simbody
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-Move to GitHub in progress ... please stand by.
+[Move to GitHub in progress.]
+
+Source code for the Simbody libraries, examples, and build system.
+
+Simbody is a high-performance, open-source toolkit for simulation of 
+articulated mechanisms, including biological structures, robots, vehicles,
+machines, etc. Simbody includes a multibody dynamics library for modeling
+motion in internal coordinates in O(n) time.
+
+Read more about it here: https://simtk.org/home/simbody