Merge pull request #39 from sutra/develop

Specify openjdk6 in travis. Remove dependency on java 1.7. Fix travis build for pull requests.
Generate nonce and send the message in a synchronized block
Generate nonce before the message is created.
Add tests
remove call on System.out
HttpStatusIOException: include http status code in message
fix a potential NPE
Merge branch 'rafalkrupinski-nonce' into develop