added vertx heroku gradle example

heroku-gradle-example/Procfile

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+web: java -Dserver.port=$PORT $JAVA_OPTS -jar build/libs/*.jar

heroku-gradle-example/README.md

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+# Vert.x Heroku Example
+
+This project shows how to deploy a Vert.x 3 applications to Heroku. The same application can be deployed using 3 approaches:
+
+you must to execute
+
+heroku config:set GRADLE_TASK="shadowJar"
+
+to configure task build.
+
+## Git
+
+Follow these steps to deploy with Git.
+
+```sh-session
+$ git clone https://github.com/vert-x3/vertx-examples
+$ heroku create
+$ heroku config:set GRADLE_TASK="shadowJar"
+$ git push heroku master
+```
+

heroku-gradle-example/build.gradle

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+plugins {
+  id 'java'
+  id 'application'
+  id 'com.github.johnrengelman.shadow' version '1.2.3'
+}
+
+repositories {
+  mavenCentral()
+  maven {
+    url "https://oss.sonatype.org/content/repositories/iovertx-3750/"
+  }
+}
+
+version = '3.5.1'
+sourceCompatibility = '1.8'
+mainClassName = 'io.vertx.core.Launcher'
+def mainVerticleName = 'io.vertx.example.HelloWorldVerticle'
+
+dependencies {
+  compile "io.vertx:vertx-core:$version"
+}
+
+shadowJar {
+  classifier = 'fat'
+  manifest {
+    attributes 'Main-Verticle': 'io.vertx.example.HelloWorldVerticle'
+  }
+  mergeServiceFiles {
+    include 'META-INF/services/io.vertx.core.spi.VerticleFactory'
+  }
+}
+
+task copyToLib(type: Copy) {
+    into "$buildDir/lib"
+    from(configurations.compile)
+}
+
+copyToLib.dependsOn(shadowJar)
+
+task wrapper(type: Wrapper) {
+  gradleVersion = '4.0'
+}

heroku-gradle-example/gradle/wrapper/gradle-wrapper.properties

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+#Sun Jun 18 19:03:02 CEST 2017
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.0-bin.zip

heroku-gradle-example/settings.gradle

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+if (!JavaVersion.current().java8Compatible) {
+  throw new IllegalStateException('''A Haiku:
+                                    |  This needs Java 8,
+                                    |  You are using something else,
+                                    |  Refresh. Try again.'''.stripMargin())
+}

heroku-gradle-example/src/main/java/io/vertx/example/HelloWorldVerticle.java

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+package io.vertx.example;
+
+import io.vertx.core.AbstractVerticle;
+import io.vertx.core.Vertx;
+
+/**
+ * @author <a href="http://tfox.org">Tim Fox</a>
+ */
+public class HelloWorldVerticle extends AbstractVerticle {
+
+  @Override
+  public void start() {
+    // Create an HTTP server which simply returns "Hello World!" to each request.
+    vertx.createHttpServer().requestHandler(req -> req.response().end("Hello World!")).listen(Integer.getInteger("server.port"), System.getProperty("http.address", "0.0.0.0"));
+  }
+}