message: Update travis: no beta/nightly, better caching
diff: language: rust
  +
  rust:
  - 1.37.0
  - stable
  - - beta
  - - nightly
  +
  jobs:
  - allow_failures:
  - - rust: nightly
  fast_finish: true
  -cache: cargo
  \ No newline at end of file
  +cache:
  + cargo: true
  + directories:
  + ~/.rustup
  + ~/.cargo
  + $TRAVIS_BUILD_DIR/target
  