Set default Kubernetes version to v1.13.2 (latest stable)

Makefile

@@ -215,9 +215,13 @@ checksum:
 
 .PHONY: clean
 clean:
-	rm -rf $(BUILD_DIR)
+	rm -rf $(BUILD_DIR)/*
 	rm -f pkg/minikube/assets/assets.go
 
+.PHONY: tmpfs-out
+tmpfs-out:
+	mount -t tmpfs -o size=10g tmpfs $(BUILD_DIR)/out
+
 .PHONY: gendocs
 gendocs: out/docs/minikube.md
 

pkg/minikube/constants/constants.go

@@ -127,7 +127,7 @@ kubectl: {{.Kubeconfig}}`
 var DefaultIsoUrl = fmt.Sprintf("https://storage.googleapis.com/%s/minikube-%s.iso", minikubeVersion.GetIsoPath(), minikubeVersion.GetIsoVersion())
 var DefaultIsoShaUrl = DefaultIsoUrl + ShaSuffix
 
-var DefaultKubernetesVersion = "v1.12.4"
+var DefaultKubernetesVersion = "v1.13.2"
 
 var ConfigFilePath = MakeMiniPath("config")
 var ConfigFile = MakeMiniPath("config", "config.json")