Include link to kentwait's fork

Author: jschaul

README.md

@@ -1,3 +1,11 @@
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+# !WARNING!
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+This library is out of date - it only works with simpy version 2 and python version 2 and the code has not changed since 2010. 
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+**For a more up to date version please check out the fork at [https://github.com/kentwait/nxsim](https://github.com/kentwait/nxsim)**
+
+
 # ComplexNetworkSim
 
 ComplexNetworkSim is a Python package for the simulation of agents connected in a complex network.