Generate source and javadoc jars.

Issue #3

build.gradle

@@ -40,6 +40,9 @@ publishing {
     publications {
         mavenJava(MavenPublication) {
             from components.java
+
+            artifact sourcesJar { classifier 'sources' }
+            artifact javadocJar { classifier 'javadoc' }
         }
     }
     repositories {
@@ -77,3 +80,13 @@ jacocoTestReport {
     }
 }
 
+task javadocJar(type: Jar) {
+    classifier = 'javadoc'
+    from javadoc
+}
+
+task sourcesJar(type: Jar) {
+    classifier = 'sources'
+    from sourceSets.main.allSource
+}
+