travis: update go versions

.travis.yml

@@ -4,12 +4,12 @@ install:
   - go get -d -t -v ./... && go build -v ./...
 
 go:
-  - 1.8
-  - 1.9
+  - 1.8.x
+  - 1.9.x
 
 script:
   - go vet ./...
   - go test -v -coverprofile=coverage.txt -covermode=atomic
 
 after_success:
-  - bash <(curl -s https://codecov.io/bash)
+  - bash <(curl -s https://codecov.io/bash)