Finished up Sentiment evaluation and writing to file

Renamed SentimentEvaluator to SentimentManager as it does more than just
calculate the sentiment. It is now able to open the URL files and append
the proper sentiment to each entry. The sentiment calculations are
called for each doc from within SPIMI before the doc's stemming but
after its other normalizations. When all docs are done evaluating then
the doc sentiments are written to file by calling the Sentiment writer
method.
Note: also fixed the sentiment score formula.