added exception catching/raising code to load_stop_tags and load_tagset
added exception catching/raising code to load_stop_tags and load_tagset

ged-lab/khmer,souravsingh/khmer,ged-lab/khmer,jas14/khmer,ged-lab/khmer,Winterflower/khmer,F1000Research/khmer,Winterflower/khmer,kdmurray91/khmer,souravsingh/khmer,Winterflower/khmer,kdmurray91/khmer,jas14/khmer,souravsingh/khmer,F1000Research/khmer,F1000Research/khmer,kdmurray91/khmer,jas14/khmer