Make Travis test against multiple Rust versions, including Rust 1.25.
Make Travis test against multiple Rust versions, including Rust 1.25.

ncalexan/mentat,ncalexan/mentat,mozilla/mentat,ncalexan/mentat,ncalexan/mentat,mozilla/mentat,ncalexan/datomish,ncalexan/mentat,ncalexan/datomish,mozilla/mentat,ncalexan/mentat,mozilla/mentat,mozilla/mentat,mozilla/mentat