Added a demo of using common metadata. #192
Added a demo of using common metadata. #192

jaduimstra/nilmtk,AlexRobson/nilmtk,HarllanAndrye/nilmtk,mmottahedi/nilmtk,josemao/nilmtk,nilmtk/nilmtk,nilmtk/nilmtk,pauldeng/nilmtk