tiny nit (#307)

* Update the build.gradle

1. More comments to build.gradle
2. add the wrapper jars

* copyright & tags

* tiny nit

appengine/helloworld-new-plugins/build.gradle

@@ -38,7 +38,7 @@ apply plugin: 'com.google.cloud.tools.appengine'  // App Engine tasks
 dependencies { // Servlet for App Engine Standard -- only one of these need to be uncommented.
 //  providedCompile group: 'javax.servlet', name: 'servlet-api', version:'2.5'
   providedCompile 'javax.servlet:javax.servlet-api:3.1.0' // if java_quickstart in appengine-web.xml
-  compile 'com.google.appengine:appengine:+
+  compile 'com.google.appengine:appengine:+'
 // Add your dependencies here.
 
 }