Merge pull request #1 from grouplens/master

sync with grouplens/lenskit
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of https://github.com/grouplens/lenskit
Merge branch 'master' of https://github.com/grouplens/lenskit
Make ThresholdTruncator injectable
Make root JavaDoc run last
Make site upload log an error, but not fail the build
Test equivalence of snapshotting user-user CF (#580)
Upload CI deployment env vars
Properly emit site upload errors
Remove unused 'release' method on TT data sets
Add isolation group IDs to TT data sets.
Generate isolated data sets from the crossfold task
Isolate data sets in different groups
Improve caching of specialized DAOs in evaluator

- Introduce common wrapping/cache logic for prefetching DAOs
- Use soft memoization for wrapper DAOs
- Retain event DAO reference in external eval job
Add commons-compress dependency (#556)
Use commons-compress for gzip compression (#556)
set encoding for JavaDoc
Enable XZ support (#556)
Test compression support in file utils