Update formatting task on Travis

.travis.yml

@@ -20,16 +20,13 @@ matrix:
       before_script:
         - rustup component add rustfmt-preview
       script:
-        - cargo fmt --all -- --write-mode=diff
-    - env:
-        - NAME='clippy'
-        # use env so updating versions causes cache invalidation
-        - CLIPPY_VERSION=0.0.200
-      rust: nightly-2018-05-14
+        - cargo fmt --all -- --check
+    - env: NAME='clippy'
+      rust: nightly-2018-07-22
       before_script:
-        - cargo install clippy --version $CLIPPY_VERSION || echo "clippy already installed"
+        - rustup component add clippy-preview
       script:
-        - cargo clippy --all -- -D clippy
+        - cargo clippy --all --all-features -- -D clippy
     - env: NAME='kcov'
       sudo: required # travis-ci/travis-ci#9061
       before_script: