message: Bump yaml-cpp so it builds with Visual Studio 15.8
  Version 0.6.2 of yaml-cpp does not build when using Visual Studio 15.8,
  for context see: jbeder/yaml-cpp#597
  Updating to this commit fixes the issue.
  Risk Level:
  Low
  Testing:
  bazel test //test/... on Linux.
diff: set -e
  -VERSION=0.6.2
  +# Pin to this commit to pick up fix for building on Visual Studio 15.8
  +COMMIT=0f9a586ca1dc29c2ecb8dd715a315b93e3f40f79 # 2018-06-30
  -curl https://github.com/jbeder/yaml-cpp/archive/yaml-cpp-"$VERSION".tar.gz -sLo yaml-cpp-"$VERSION".tar.gz
  -tar xf yaml-cpp-"$VERSION".tar.gz
  -cd yaml-cpp-yaml-cpp-"$VERSION"
  +curl https://github.com/jbeder/yaml-cpp/archive/"$COMMIT".tar.gz -sLo yaml-cpp-"$COMMIT".tar.gz
  +tar xf yaml-cpp-"$COMMIT".tar.gz
  +cd yaml-cpp-"$COMMIT"
  mkdir build
  cd build
  