Update README.md

Author: facontidavide

README.md

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 # BehaviorTree.ROS
-ROS related code on top of the framework BehaviorTree.CPP
+
+[BehaviorTree.CPP](https://github.com/BehaviorTree/BehaviorTree.CPP) is a __middleware independent__ framework 
+to develop Behavior Trees in C++.
+
+The library is not particularly opinionated about the way Actions and Conditions should be created; this gives
+more freedom to the developer, but can also be confusing for those people which are getting started with it.
+
+[BehaviorTree.ROS](https://github.com/BehaviorTree/BehaviorTree.ROS) provides some practical examples and 
+utilities related to [ROS (the Robotic Operative System)](http://www.ros.org).
+
+ROS users can use this library or look at the way Nodes are implemented to implmenent their own version.