message: Append C++14 standard flag instead of prepending.
  * This stops it from being overridden by the global --std=c++11 in the
  root CMakeLists.txt which ends up after it in the command line.
diff: # Build as C++14 for the python bindings template-fu
  if (CMAKE_VERSION VERSION_LESS "3.1")
  - set (CMAKE_CXX_FLAGS "--std=c++14 ${CMAKE_CXX_FLAGS}")
  + set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} --std=c++14")
  else ()
  set (CMAKE_CXX_STANDARD 14)
  endif ()
  