Leverage new Travis support for Rust

.travis.yml

@@ -1,9 +1 @@
-before_install:
-  - yes | sudo add-apt-repository ppa:hansjorg/rust
-  - yes | sudo add-apt-repository ppa:cmrx64/cargo
-  - sudo apt-get update
-install:
-  - sudo apt-get install rust-nightly cargo
-script:
-  - cargo build
-  - cargo test
+language: rust