message: refactor(CI): Explicit if-conditions
  I've seen problems with travis swallowing the leading `!`.
diff: @@ -23,8 +23,8 @@ matrix:
  install:
  - curl https://sh.rustup.rs -sSf | sh -s -- -y --default-toolchain $TRAVIS_RUST_VERSION
  - source ~/.cargo/env || true
  - - which cargo-coveralls || cargo install cargo-travis
  - - which cargo-when || cargo install cargo-when
  + - if ! which cargo-coveralls ; then cargo install cargo-travis ; fi
  + - if ! which cargo-when ; then cargo install cargo-when ; fi
  - travis_wait cargo when --channel stable install rustfmt --force --vers 0.8.3
  - travis_wait cargo when --channel nightly install clippy --force || true
  @@ -34,8 +34,8 @@ script:
  - cargo check --verbose
  - cargo check --verbose --features "syntax-highlight"
  - cargo test --verbose --features "syntax-highlight"
  - - ! which cargo-clippy || cargo when --channel nightly clippy -- --version
  - - ! which cargo-clippy || cargo when --channel nightly clippy --features "syntax-highlight"
  + - if which cargo-clippy ; then cargo when --channel nightly clippy -- --version ; fi
  + - if which cargo-clippy ; then cargo when --channel nightly clippy --features "syntax-highlight" ; fi
  - cargo when --channel stable fmt -- --version
  - cargo when --channel stable fmt -- --write-mode=diff
  