refactoring for better readability and extensibility

* stored output of previous version for regression tests
* split TestingJenaScala into JenaStatementSource, StatementContextExtractor, ContextOutputFormatter
* JenaStatementSource reads statements from a Jena Model as a Traversable (allows us to use map, etc.)
* StatementContextExtractor implements different behaviors for getting words out of statements (TODO: subclasses)
* ContextOutputFormatter deals with differences in TSV output versus Pig format