TimeFrame.adjacent now tests if either TF is empty
TimeFrame.adjacent now tests if either TF is empty

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