v0.5.0

Use serde instead of rustc_serialize.

0.4.2: Merge pull request #32 from maciejkula/fix/serialization

Fix EncodableRng JSON serialization.

0.4.1: Merge pull request #30 from maciejkula/remove_unused_import

Remove unused import in decision_tree.rs

Parallelism and Factorization Machines

Merge pull request #25 from maciejkula/parallel_predict

Parallel model fitting and prediction