Minor improvement to POSAnnotator

[borice]

Looking at code to try to understand how to use POSAnnotator I see an opportunity for a minor improvement. In

cogcomp-nlp/pos/src/main/java/edu/illinois/cs/cogcomp/pos/POSAnnotator.java

Line 94 in 49f2263

tagger.discreteValue(lbjtoken);

and line 97 the code seems to be doing the same operation tagger.discreteValue(lbjtoken). Perhaps the value can be saved the first time and reused in line 97.