Merge pull request #301 from breznak/yaml-cpp

Yaml cpp update to 0.3
Updates libyaml to 0.3 per numenta/nupic#337
Merge pull request #339 from oxtopus/yaml-cpp-darwin64

Updates libyaml to 0.3 per numenta/nupic#337
enable LLVM/Clang in Travis
fix clang operator<< argument-dependant lookup, ambiguity