Enable rpath on OS X when the CMake version supports it (#418)
Enable rpath on OS X when the CMake version supports it (#418)

CMake policy CMP0042 changes the default value of the MACOSX_RPATH target property to TRUE, therefore setting the directory portion of the install_name field of a shared library to be @rpath on OS X.
WrinklyNinja/yaml-cpp,WrinklyNinja/yaml-cpp,SimplyKnownAsG/yaml-cpp,loot/yaml-cpp,graehl/yaml-cpp,kn65op/yaml-cpp,dand-oss/yaml-cpp,loot/yaml-cpp,WaveBlocks/yaml-cpp,kn65op/yaml-cpp,kn65op/yaml-cpp,butataatawa/yaml-cpp,jbeder/yaml-cpp,graehl/yaml-cpp,kn65op/yaml-cpp,SimplyKnownAsG/yaml-cpp,SimplyKnownAsG/yaml-cpp,loot/yaml-cpp,jbeder/yaml-cpp,WrinklyNinja/yaml-cpp,dand-oss/yaml-cpp,tangrams/yaml-cpp,WrinklyNinja/yaml-cpp,jbeder/yaml-cpp,butataatawa/yaml-cpp,butataatawa/yaml-cpp,graehl/yaml-cpp,graehl/yaml-cpp,WaveBlocks/yaml-cpp,jbeder/yaml-cpp,jbeder/yaml-cpp,WaveBlocks/yaml-cpp,tangrams/yaml-cpp,loot/yaml-cpp,graehl/yaml-cpp,butataatawa/yaml-cpp,dand-oss/yaml-cpp,SimplyKnownAsG/yaml-cpp,WaveBlocks/yaml-cpp,dand-oss/yaml-cpp,tangrams/yaml-cpp,dand-oss/yaml-cpp,tangrams/yaml-cpp