Add a convenience pom for local builds and travis-ci, and alter travis-ci configuration to use it.
diff --git a/build-pom.xml b/build-pom.xml
new file mode 100644
index 0000000..bf0527f
--- /dev/null
+++ b/build-pom.xml
@@ -0,0 +1,14 @@
+<!-- A pure convenience for local builds and travis-ci. -->
+<project>
+ <modelVersion>4.0.0</modelVersion>
+ <groupId>build-only</groupId>
+ <artifactId>build-only</artifactId>
+ <version>NO_VERSION</version>
+ <packaging>pom</packaging>
+ <modules>
+ <module>.</module>
+ <module>factory</module>
+ <module>service</module>
+ <module>value</module>
+ </modules>
+</project>