Handle broken pipe or closed connection exceptions

[ramunasd]

This adresses mostly broken connection handling and proper flag/variable cleanup.

• Handle various connection problems and throw AMQPConnectionClosedException
• Fix endless loop when writing to blocked stream, i.e. unresponsive vpn connection infinite loop inside StreamIO::write, in case of broken connection #624
• Reset connection/channel state, clear callbacks so consumers knows when to stop waiting, allow reconnect, issue isConnected was still true when broken pipe or close connection in channel->wait() #389
• Write data to socket/stream split in 8k chunks - improves stability and predictability for non-blocking connections
• replace socket_read with socket_recv because latter do not mix read data with syscall output therefore error handling becomes easier
• introduce https://github.com/Shopify/toxiproxy, add tests for blocked/closed connections, those skipped on travis cause need to figure out how to run proxy there
• minor non-functional & code style improvements

I know this one is quite big Nonetheless this would be good improvement for release 2.9.0

[lukebakken]

Thanks!