Report rating distributions from OrdRec
Output rating predictions with channels

- Add predict command (#501)
- Add toString to Vec
- Add logging to OrdRec
Add more logging to OrdRec
Fix type errors in Predict
Make OrdRec use vectorz (#503)
Make preference domain quantizer use vectorz
Fix tests for preference domain quantizer
Add OrdRec to relesae notes
Bump to Grapht 0.7.0 release
Update 2.1 release notes
Document status files
[maven-release-plugin] prepare release lenskit-2.1-M1
[maven-release-plugin] prepare for next development iteration
Fix broken POM
Little crossfold cleanups
Introduce crossfold method configuration
Implement user sampling (#512)
Add toString to CSVDataSource
Merge pull request #513 from elehack/feature/elehack-412-sampling-crossfold

Implement sampling-based crossfolding (closes #412)
Merge https://github.com/grouplens/lenskit