Include success of Javadoc gen. in test outcome.

Documentation is important; so if the Javadoc generator barfs for a
serious reason, which I know it will for JDK 8, we want to know.

Author: matttproud

Makefile.TRAVIS

@@ -13,5 +13,6 @@ utility: client
 
 test: build
 	mvn test
+	mvn javadoc:aggregate
 
 .PHONY: build client examples test utility