Support loggregator-based logging
Merge branch 'loggregator'
Update travis config to install protobuf-compiler
Run 'mvn install' in top-level directory to build test apps
Install libprotobuf-dev as well
Print protoc version for debugging
apt-get update before installing protobuf
Attempt to fix websocket daemon issue through tomcat snapshot version
Gracefully allow clients to exit when the server-side closes the websocket

- Use tomcat snapshot version that fixes the issue with a lingering thread
- Use daemon thread for the heartbeat timer

Also fixed an issue where the session may have been closed by the time
the message handler is added by moving the code that add the handler
in Endpoint.onOpen implementation.
Changed RestLogCallback listeners to a set to avoid registering the same
listener again.
Merge pull request #159 from nierajsingh/master

Changed RestLogCallback listeners to a set