better error message for unexpected category, close #314
better error message for unexpected category, close #314

pombredanne/dedupe,neozhangthe1/dedupe,datamade/dedupe,dedupeio/dedupe,davidkunio/dedupe,tfmorris/dedupe,pombredanne/dedupe,dedupeio/dedupe,datamade/dedupe,tfmorris/dedupe,nmiranda/dedupe,nmiranda/dedupe,01-/dedupe,01-/dedupe,davidkunio/dedupe,neozhangthe1/dedupe