msvs - must include header to use std::string

msvs - must include <string> header. Otherwise we get funny compiler errors like


Error 5 error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' d:\program files\microsoft visual studio 10.0\vc\include\xfunctional 125 1 cpp_consoleTest