Link to C++ extensions in README.md (pytorch#8737)

README.md

@@ -141,9 +141,8 @@ and with minimal abstractions.
 You can write new neural network layers in Python using the torch API
 [or your favorite NumPy-based libraries such as SciPy](http://pytorch.org/tutorials/advanced/numpy_extensions_tutorial.html).
 
-If you want to write your layers in C/C++, we provide an extension API based on
-[cffi](http://cffi.readthedocs.io/en/latest/) that is efficient and with minimal boilerplate.
-There is no wrapper code that needs to be written. You can see [a tutorial here](http://pytorch.org/tutorials/advanced/c_extension.html) and [an example here](https://github.com/pytorch/extension-ffi).
+If you want to write your layers in C/C++, we provide a convenient extension API that is efficient and with minimal boilerplate.
+There is no wrapper code that needs to be written. You can see [a tutorial here](http://pytorch.org/tutorials/advanced/cpp_extension.html) and [an example here](https://github.com/pytorch/extension-cpp).
 
 
 ## Installation