Added note about properties plugin

Author: rjrudin

examples/sample-project/build.gradle

@@ -7,6 +7,9 @@ buildscript {
      * set when calling Gradle. For example, you could run "gradle -Penv=qa mlDeploy" in order to apply the env-qa.gradle
      * build file, which would set properties based on the QA environment. This doesn't have anything to do with ml-gradle -
      * it just shows one technique for overriding properties. See env-prod.gradle and env-qa.gradle for more details. 
+     *
+     * Also see https://github.com/stevesaliman/gradle-properties-plugin for an elegant way of supporting properties files
+     * for different environments.
      */
     if (project.hasProperty("env")) {
         def buildFile = "env-" + project.property("env") + ".gradle"
@@ -19,6 +22,9 @@ buildscript {
      * development. A developer can create a non-version-controlled local.gradle file and, within that file, override any
      * properties that are defined in gradle.properties. This also isn't specific to ml-gradle - it's just one way with
      * Gradle to allow a developer to easily override gradle.properties for local development purposes. 
+     *
+     * Also see https://github.com/stevesaliman/gradle-properties-plugin for an elegant way of supporting properties files
+     * for different environments.
      */
     if (new File("local.gradle").exists()) {
         println "Applying local.gradle file"