Polish "Improve ExitCodeGenerator doc"

Closes gh-9740

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -337,29 +337,30 @@ be used.
 
 In addition, beans may implement the `org.springframework.boot.ExitCodeGenerator`
 interface if they wish to return a specific exit code when `SpringApplication.exit()`
-is called. This exit code can then be passed to `System.exit()` to pass it to the outside.
+is called. This exit code can then be passed to `System.exit()` to return it as a status
+code.
 
 [source,java,indent=0]
 ----
 	@SpringBootApplication
-    public class ExitCodeApplication {
+	public class ExitCodeApplication {
 
-    	public static void main(String[] args) {
-    		System.exit(SpringApplication.exit(SpringApplication.run(ExitCodeApplication.class, args)));
-    	}
+		public static void main(String[] args) {
+			System.exit(SpringApplication.exit(
+					SpringApplication.run(ExitCodeApplication.class, args)));
+		}
 
-    	@Bean
-    	public ExitCodeGenerator exitCodeGenerator(){
-    		return () -> 42;
-    	}
+		@Bean
+		public ExitCodeGenerator exitCodeGenerator(){
+			return () -> 42;
+		}
 
-    }
+	}
 ----
 
-Also, the `ExitCodeGenerator` interface may be implemented by exceptions. When such an exception is
-encountered, Spring Boot will return the exit code provided by the implemented `getExitCode()` method
-to the outside caller.
-
+Also, the `ExitCodeGenerator` interface may be implemented by exceptions. When such an
+exception is encountered, Spring Boot will return the exit code provided by the
+implemented `getExitCode()` method.
 
 
 [[boot-features-application-admin]]

spring-boot/src/main/java/org/springframework/boot/ExitCodeGenerator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2016 the original author or authors.
+ * Copyright 2012-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,8 +18,7 @@ package org.springframework.boot;
 
 /**
  * Interface used to generate an 'exit code' from a running command line
- * {@link SpringApplication}. Since 1.3.2 this interface can be used on exceptions as well
- * as directly on beans.
+ * {@link SpringApplication}. Can be used on exceptions as well as directly on beans.
  *
  * @author Dave Syer
  * @see SpringApplication#exit(org.springframework.context.ApplicationContext,