yaml-cpp: incorporated recipe from Kartik Mohta's repository

This commit adds the yaml-cpp recipe from the repository at
https://github.com/kartikmohta/meta-km. The file is licensed
with the MIT license
(cf. https://github.com/kartikmohta/meta-km/blob/master/LICENSE).

The original recipe can be found at
https://github.com/kartikmohta/meta-km/blob/master/recipes-devtools/yaml-cpp/yaml-cpp_0.3.0.bb

The README file acknowledges Kartik Mohta's contribution and names
him as a contributor.
Merge pull request #117 from bulwahn/yaml-cpp

yaml-cpp: incorporated recipe from Kartik Mohta's repository