removes Travis CI (#333)

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

.travis.yml

@@ -1,68 +0,0 @@
-language: rust
-
-env:
-  - RUSTFLAGS="-D warnings"
-
-# Cache the whole `~/.cargo` directory to keep `~/cargo/.crates.toml`.
-cache:
-  directories:
-    - /home/travis/.cargo
-
-# Don't cache the cargo registry because it's too big.
-before_cache:
-  - rm -rf /home/travis/.cargo/registry
-
-
-branches:
-  only:
-    - master
-    - staging
-    - trying
-
-matrix:
-  fast_finish: true
-  include:
-    - rust: nightly
-      os: linux
-
-    - rust: nightly
-      os: osx
-      osx_image: xcode9.2
-
-    - rust: nightly-x86_64-pc-windows-msvc
-      os: windows
-
-    - name: fmt
-      rust: nightly
-      os: linux
-      before_script: |
-        if ! rustup component add rustfmt; then
-          target=`curl https://rust-lang.github.io/rustup-components-history/x86_64-unknown-linux-gnu/rustfmt`;
-          echo "'rustfmt' is unavailable on the toolchain 'nightly', use the toolchain 'nightly-$target' instead";
-          rustup toolchain install nightly-$target;
-          rustup default nightly-$target;
-          rustup component add rustfmt;
-        fi
-      script:
-        - cargo fmt --all -- --check
-
-    - name: docs
-      rust: nightly
-      os: linux
-      script:
-        - cargo doc --features docs
-
-    - name: book
-      rust: nightly
-      os: linux
-      before_script:
-        - test -x $HOME/.cargo/bin/mdbook || ./ci/install-mdbook.sh
-        - cargo build # to find 'extern crate async_std' by `mdbook test`
-      script:
-        - mdbook build docs
-        - mdbook test -L ./target/debug/deps docs
-
-script:
-  - cargo check --all --benches --bins --examples --tests
-  - cargo check --features unstable --all --benches --bins --examples --tests
-  - cargo test --all --doc --features unstable