.travis.yml: Add '-set_exit_status' to golint invocation

So Travis tells us when golint finds something suspicious.

Signed-off-by: W. Trevor King <[email protected]>

Author: wking

.travis.yml

@@ -22,7 +22,7 @@ install: true
 
 script:
   - go vet -x ./...
-  - golint ./...
+  - golint -set_exit_status ./...
   - go build .
   - go test -v ./...
   - ./git-validation -run DCO,short-subject,dangling-whitespace -v