Sentiment Analysis Example

Added a movie review sentiment analysis example. After making this
example I decided to use it as the baseline test for improvements to
the classifiers in future releases.

Improved the Vector Space Model by using TF-IDF weight vectors. This
significantly improved the quality of the classifier.

After 200 training examples the test classification success is roughly
60%. At 600 training examples the test classification success is
roughly 80%.

70% success is the success ratio for humans performing the
classification.