GH-65: Add polled-consumer Sample

Resolves https://github.com/spring-cloud/spring-cloud-stream-samples/issues/65

Polishing - PR Comments

- add docker-compose
- change runner to process multiple messages

processor-samples/polled-consumer/docker-compose.yml

@@ -0,0 +1,19 @@
+version: '3'
+services:
+    kafka:
+      image: wurstmeister/kafka
+      container_name: kafka-polledconsumer
+      ports:
+        - "9092:9092"
+      environment:
+        - KAFKA_ADVERTISED_HOST_NAME=127.0.0.1
+        - KAFKA_ADVERTISED_PORT=9092
+        - KAFKA_ZOOKEEPER_CONNECT=zookeeper:2181
+      depends_on:
+        - zookeeper
+    zookeeper:
+      image: wurstmeister/zookeeper
+      ports:
+        - "2181:2181"
+      environment:
+        - KAFKA_ADVERTISED_HOST_NAME=zookeeper