Two mostly aesthetic fixes. First, Travis moved a method call in
DocumentProcessor and as a result the progress window was not appearing
until after initial feature extraction. Second, the new version of
JStylo adds an author named "_Unknown_" to the Weka training instances,
even if this author has no documents. This extra author caused the
results graph to be drawn incorrectly. I increased the number of authors
in the chart as a temporary workaround until I can find a good way to
remove or hide the _Unknown_ author.