change some variable names and documentation text in prune_lm_dir.py
change some variable names and documentation text in prune_lm_dir.py

wantee/pocolm,chris920820/pocolm,chris920820/pocolm,keli78/pocolm,wantee/pocolm,wantee/pocolm,keli78/pocolm,chris920820/pocolm,chris920820/pocolm,keli78/pocolm,keli78/pocolm,wantee/pocolm