Create udp_agent.rb

This is my second attempt to create an agent.
This one is to use the UDP protocol to send data around.
I used the post_agent as an example for this agent.

It is quite a naive an simplistic way to create a udp connection.
I tested it with netcat as a udp server, hence it probably require some more thorough testing.

My lack of knowledge of rspec means that there is no test shipped with it.
I'm on freenode #huginn to discuss it further if needed.