rename AMQPConnection to Abstract connection

This commit is needed to make blame works nice after all changes
add possibility to work with NO_DELAY sockets

Using sockets without NO_DELAY option causes extreme lack of
performance in some cases (for example RPC calls and responses).

There is no possibility to set NO_DELAY option when working with streams, so
AMQPSocketConnection class was added with some minor refactoring

See benchmark for performance comparison between socket and stream connections
add some functional tests for socket connection
socket benchmark fixes
Merge pull request #65 from StartupLabs/no_delay_sockets

add possibility to work with NO_DELAY sockets