Added more explanation to OptimizationException in BFGS.
Added more explanation to OptimizationException in BFGS.

steveash/Mallet,lewg/Mallet,steveash/Mallet,lewg/Mallet,ohjeyong/mallet,carschno/Mallet,RWArunde/Mallet,zxsted/Mallet,steveash/Mallet,ohjeyong/mallet,carschno/Mallet,carschno/Mallet,RWArunde/Mallet,palm-toolkit/Mallet,palm-toolkit/Mallet,zxsted/Mallet,ohjeyong/mallet,zxsted/Mallet,lewg/Mallet,RWArunde/Mallet