In order to test some of the internals, split them into Binding.h.
This makes the interface visible for tests. The implementation
still lives in the same place.
While here, adjust the test to the changed **example** which
now lists an additional variable.
- Use only utils/YamlUtils.h to pull in yaml-cpp and supporting code.
- When compiling with clang, turn off warnings that the system header
for yaml-cpp would generate.
