Added new interface to attach_atmosphere() that uses memory-safe C++11 pointers (std::unique_ptr<>).  In general, the g++ flag --std=c++11 should be used with C++11 code; however, no changes needed to be made to the CMake stuff to get this to work on my setup.  I was not able to verify the command lines make uses to compile.  At some point, this change should be propagated elsewehre in the code, or ripped out based on a decision to NOT use this kind of C++ idiom.