Allow mutable index mappings to be frozen (#443)
Small packed preference build cleanups

- Rename builder to Builder to better match LensKit patterns
- Use configured RNG for shuffling
Add id mapping -> vector conversion (#443)

Add method to Vectors to convert index mappings and arrays to sparse vectors.
Use new index mappings in preference snapshot (#443)

- Update preference snapshots to use id index mappings
- Update FunkSVD and least-squares to use id index mappings
Fix lots of warnings
Set the RNG on the algorithm instance builder
Fix Java 8 build
Disable Java 8 builds in Travis (#466)
Fix NPE in algorithm instance builder
Report the the source of scores (#444)

- Add ScoreSource to indicate source of scores
- Report score source from fallback item scorer
- Report score source from simple rating predictor
add missing license header
Use Python/Pandas to build charts (#390)
improve fancy archetype tests for pandas (#390)
add python-tk to unbreak matplotlib (#390)
Drop lenskit-test dep from maven plugin
Set matplotlib backend (#390)
use backend before importing pyplt
Install LaTeX for integration tests
Merge pull request #465 from elehack/feature/elehack-cleanup

Merge in Michael's cleanups and new fixes.