Changed logging to slf4j. This will be needed for later support for
Apache Mina.
Decided to use netty instead of mina after a nice advice of a co-worker.
Added an abstract message for communication. All messages sent over
network should extend this class.
Better javadoc.
Added JUnit and Hamcrest
Added file for network documentation.
Changed AbstractNetworkMessage because we can't just create a new
ByteBuf.