When running go fmt, match all Golang patch versions

.travis.yml

@@ -27,7 +27,7 @@ script:
 - make test
 - make vet
 - make errcheck
-- if [ "$TRAVIS_GO_VERSION" = "1.11" ]; then make fmt; fi
+- if [[ "$TRAVIS_GO_VERSION" == 1.11* ]]; then make fmt; fi
 
 after_success:
 - bash <(curl -s https://codecov.io/bash)