Use properties for source inclusion

This allows people to override the build configuration to use a
different source directory, and the sources will still be included in
the JAR by default.

And while at it, let's include the test sources in the test JAR, too!

pom.xml

@@ -29,9 +29,14 @@
 	<build>
 		<resources>
 			<resource>
-				<directory>src/main/java</directory>
+				<directory>${project.build.sourceDirectory}</directory>
 			</resource>
 		</resources>
+		<testResources>
+			<testResource>
+				<directory>${project.build.testSourceDirectory}</directory>
+			</testResource>
+		</testResources>
 		<plugins>
 			<plugin>
 				<groupId>org.codehaus.mojo</groupId>