Improved error messages.
Improved error messages.

Maluuba/crfsuite,prateek05/crfsuite,dmit25/crfsuite,dmit25/crfsuite,dmit25/crfsuite,ExpResults/partial-crfsuite,prateek05/crfsuite,abicky/crfsuite,ExpResults/partial-crfsuite,Maluuba/crfsuite,prateek05/crfsuite,Maluuba/crfsuite,prateek05/crfsuite,Maluuba/crfsuite,Maluuba/crfsuite,abicky/crfsuite,prateek05/crfsuite,ExpResults/partial-crfsuite,ExpResults/partial-crfsuite,dmit25/crfsuite,abicky/crfsuite,abicky/crfsuite,ExpResults/partial-crfsuite,abicky/crfsuite,prateek05/crfsuite,abicky/crfsuite,Maluuba/crfsuite,dmit25/crfsuite,dmit25/crfsuite,ExpResults/partial-crfsuite,abicky/crfsuite,prateek05/crfsuite