INTSAMPLES-57 Update README.md

For reference: https://jira.springsource.org/browse/INTSAMPLES-57

* reflect the correct Main class to be used
* add exec-maven-plugin and add usage to README.md

basic/xml/README.md

@@ -8,7 +8,11 @@ This example demonstrates the following aspects of the XML support available wit
 3. XPath Expression - which tests to see if the order item is in stock
 3. XSLT Transformer - to transform the payload of the order message into a resupply message where the order item is found to be out of stock.
 
-To run sample simply execute **BookOrderProcessingTest**. You should see the following output:
+To run the sample execute class **org.springframework.integration.samples.xml.BookOrderProcessingTestApp**. With Maven you can run the sample by executing:
+
+    $ mvn clean package exec:java
+
+You should see the following output:
 
 	INFO : org.springframework.integration.samples.xml.WarehouseDispatch - Warehouse dispatching orderItem: 
 	<?xml version="1.0" encoding="UTF-8" standalone="no"?>

basic/xml/pom.xml

@@ -45,6 +45,14 @@
 					<showDeprecation>false</showDeprecation>
 				</configuration>
 			</plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>1.2</version>
+                <configuration>
+                    <mainClass>org.springframework.integration.samples.xml.BookOrderProcessingTestApp</mainClass>
+                </configuration>
+            </plugin>
 		</plugins>
 	</build>
     <repositories>