Do not start application context automatically

- This will avoid other lifecycle beans inside the application context starting when
binding lifecycle beans are started.

Resolves #525

Address review comments

spring-cloud-stream-core-docs/src/main/asciidoc/spring-cloud-stream-overview.adoc

@@ -386,7 +386,6 @@ public class SendingBean {
     }
 }
 ----
-
 ==== Producing and Consuming Messages
 
 You can write a Spring Cloud Stream application using either Spring Integration annotations or Spring Cloud Stream's `@StreamListener` annotation.