Introduce types for UserID, ItemId and U2IAction
Enforce immutable collections in API
Merge pull request #5 from jeantil/types

Introduce types for UserID, ItemId and U2IAction
Remove oracle jdk6 target

Remove the Oracle jdk6 as it is in EOL and no more supported by travis-CI
Merge pull request #6 from jeantil/immutable_collections

Enforce immutable collections in API
Add specialized exceptions to the API
Properly read prediction results
SBT 0.13.2-RC1 for improved incremental compilation