message: Allow master version to be set from config
diff: // Copyright 2016-2018, Pulumi Corporation. All rights reserved.
  +import * as gcp from "@pulumi/gcp";
  import { Config } from "@pulumi/pulumi";
  const config = new Config();
  @@ -17,4 +18,4 @@ export const clusterNodeCount = config.getNumber("clusterNodeCount") || 3;
  export const clusterNodeMachineType = config.get("clusterNodeMachineType") || "n1-standard-1";
  export const clusterUsername = config.get("clusterUsername") || "admin";
  export const clusterPassword = config.require("clusterPassword");
  -export const masterVersion = config.require("masterVersion");
  +export const masterVersion = config.get("masterVersion") || gcp.container.getEngineVersions().latestMasterVersion;
  