Merge pull request #41 from epage/ci

chore: Update CI

.travis.yml

@@ -1,25 +1,25 @@
 sudo: false
 language: rust
 rust:
-- 1.22.0  # Two releases back
+- 1.22.0  # Oldest supported version
 - stable
 - beta
 - nightly
 matrix:
   include:
   - env: RUSTFMT
-    rust: 1.25.0  # `stable`: Locking down for consistent behavior
+    rust: 1.27.0  # `stable`: Locking down for consistent behavior
     install:
       - rustup component add rustfmt-preview
     script:
       - cargo fmt -- --write-mode=diff
   - env: RUSTFLAGS="-D warnings"
-    rust: 1.25.0  # `stable`: Locking down for consistent behavior
+    rust: 1.27.0  # `stable`: Locking down for consistent behavior
     install:
     script:
     - cargo check --tests --all-features
-  - env: CLIPPY_VERSION="0.0.179"
-    rust: nightly-2018-01-12
+  - env: CLIPPY_VERSION="0.0.209"
+    rust: nightly-2018-06-19
     install:
       - travis_wait cargo install clippy --version $CLIPPY_VERSION || echo "clippy already installed"
     script: