[README] add acknowledgement

Author: proyan

README.md

@@ -7,3 +7,7 @@ PyCppAD — Python bindings for CppAD Automatic Differentiation library
 
 **PyCppAD** is an open source framework which provides bindings for the CppAD Automatic Differentiation([CppAD](https://coin-or.github.io/CppAD/doc/cppad.htm)) C++ library in Python.
 **PyCppAD** also includes support for the CppADCodeGen ([CppADCodeGen](https://github.com/joaoleal/CppADCodeGen)), C++ library, which exploits CppAD functionality to perform code generation.
+
+## Acknowledgments
+
+The development of **PyCppAD** is supported by the [Willow team](https://www.di.ens.fr/willow/) [@INRIA](http://www.inria.fr).