Make "unix-dgram" optional dependancy, add queue limit and fix TCP protocol

Hi there. Earlier I already submitted unix-dgram fix. Somebody answered that you will do something better in #22, but finally it became something different and issues is exist. Optional dependency is absolutely safe thing. System that will have it will work, other (solaris) will not fail.
Next to that we was need to use TCP protocol and it appears to be not working. There is no message delimiters (LF). Additionally to avoid memory overuse we add limit for message queue. Hop you find it useful.