Merge pull request #3 from switchgears/master

Listen to event bus and send UDP messages from events on this
Get rid of warning while instantiating singleton classes
Add a ZeroMQ message handler.

This will allow remote lamps sitting behind a firewall to poll the
Jenkins server as often as they like.
Using normal HTTP request would be too costly in case many lamps
were deployed for a single master. Using a message queuing system,
especially a fast one such as ZeroMQ, solves this problem.
Fix several errors in the ZeroMQ usecase
Merge remote-tracking branch 'jenkins/master' into async-update

Conflicts:
    src/main/java/org/jenkinsci/plugins/extremefeedback/EventMessageHandler.java
    src/main/java/org/jenkinsci/plugins/extremefeedback/Lamps.java