Add README.md in c++11_cuda example

Author: harrism

.gitignore

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-c++11_cuda
+c++11_cuda/c++11_cuda

c++11_cuda/README.md

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+# Example of C++11 in CUDA device code
+
+This code depends on [cpp11-range](https://github.com/harrism/cpp11-range) as a submodule.  Before building, you need to run the following commands from the "code-samples" base directory (parent of this example):
+
+    git submodule init
+    git submodule update
+