Added missing Javadoc tags.

src/main/java/envoy/data/MessageIdGenerator.java

@@ -20,6 +20,7 @@ public class MessageIdGenerator {
 	 *
 	 * @param begin the first ID
 	 * @param end   the last ID
+	 * @since Envoy Common v0.2-alpha
 	 */
 	public MessageIdGenerator(long begin, long end) {
 		current		= begin;
@@ -28,11 +29,13 @@ public class MessageIdGenerator {
 
 	/**
 	 * @return {@code true} if there are unused IDs remaining
+	 * @since Envoy Common v0.2-alpha
 	 */
 	public boolean hasNext() { return current < end; }
 
 	/**
 	 * @return the next ID
+	 * @since Envoy Common v0.2-alpha
 	 */
 	public long next() {
 		if (!hasNext()) throw new IllegalStateException("All IDs have been used");