message: error on incorrect c++ standards, remove guard that is no longer needed
diff: # Register the sol library for parsing lua
  #------------------------------------------------------------------------------
  -if (LUA_FOUND AND (NOT BLT_CXX_STD STREQUAL "c++11"))
  +if (LUA_FOUND)
  blt_add_library(NAME sol
  HEADERS axom/sol.hpp)
  