Using the maven flatten plugin for published POMs

To avoid propagating build setup that is required to build a Spring Cloud project, the maven flatten plugin can be used. It has the advantage of letting you use whatever features you need while publishing "clean" pom to the repository.

fixes gh-89

docs/src/main/asciidoc/README.adoc

@@ -42,6 +42,24 @@ $ mvn deploy -P central -DaltReleaseDeploymentRepository=sonatype-nexus-staging:
 
 include::https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/docs/src/main/asciidoc/contributing.adoc[]
 
+== Flattening the POMs
+
+To avoid propagating build setup that is required to build a Spring Cloud project, we're using the maven flatten plugin. It has the advantage of letting you use whatever features you need while publishing "clean" pom to the repository.
+
+In order to add it, add the `org.codehaus.mojo:flatten-maven-plugin` to your `pom.xml`.
+
+[source,xml]
+----
+<build>
+    <plugins>
+        <plugin>
+            <groupId>org.codehaus.mojo</groupId>
+            <artifactId>flatten-maven-plugin</artifactId>
+        </plugin>
+    </plugins>
+</build>
+----
+
 == Reusing the documentation
 
 Spring Cloud Build publishes its `spring-cloud-build-docs` module that contains