Support Broker Bridge Now!
Change: rename project from 'emqtt' to 'emqttd'
Change: lager:debug to dump RECV/SENT packets
Feature: emqttd_bridge, emqttd_bridge_sup to support broker bridge
Feature: emqtt_event to publish client connected/disconnected message to $SYS topics
Feature: ./bin/emqttd_ctl add more commands: listeners, broker, bridges, start_bridge, stop_bridge...
Feature: issue#57 - support to configure max packet size
Feature: issue#68 - if sys_interval = 0, emqttd_broker will not publish messages to $SYS/brokers/#
Bugfix: issue#67 - subscribe '#' to receive all messages
Bugfix: issue#64 - emqtt_app start/2: should wait_for_databases
Test: emqttd_topic_tests add more '_match_test'