chore(ci): update CI to Rust 1.38, modern rustfmt/clippy

Signed-off-by: Nick Stevens <[email protected]>

Author: nastevens

.travis.yml

@@ -7,23 +7,23 @@ rust:
 - nightly
 matrix:
   include:
-  - env: RUSTFMT
-    rust: 1.25.0  # `stable`: Locking down for consistent behavior
+  - name: check rustfmt
+    rust: 1.38.0  # `stable`: Locking down for consistent behavior
     install:
-      - rustup component add rustfmt-preview
+      - rustup component add rustfmt
     script:
-      - cargo fmt -- --write-mode=diff
-  - env: RUSTFLAGS="-D warnings"
-    rust: 1.25.0  # `stable`: Locking down for consistent behavior
-    install:
+      - cargo fmt --all -- --check
+  - name: check with -D warnings
+    env: RUSTFLAGS="-D warnings"
+    rust: 1.38.0  # `stable`: Locking down for consistent behavior
     script:
     - cargo check --tests --all-features
-  - env: CLIPPY_VERSION="0.0.179"
-    rust: nightly-2018-01-12
+  - name: check clippy
+    rust: 1.38.0  # `stable`: Locking down for consistent behavior
     install:
-      - travis_wait cargo install clippy --version $CLIPPY_VERSION || echo "clippy already installed"
+      - rustup component add clippy
     script:
-      - cargo clippy --all-features -- -D clippy
+      - cargo clippy --all --all-features -- -D warnings
 
 install:
 - rustc -Vv