travis: more strict golint

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

.travis.yml

@@ -15,5 +15,5 @@ install: true
 
 script:
   - go vet -x ./...
-  - golint ./...
+  - golint -set_exit_status ./...
   - go test -v ./...

cmd/gomtree/main.go

@@ -78,7 +78,7 @@ func main() {
 	}
 
 	// -p <path>
-	var rootPath string = "."
+	var rootPath = "."
 	if *flPath != "" {
 		rootPath = *flPath
 	}