NanoMQ v0.8.3 Release Note

This is a bug-fix release for 0.8.0

1. New packaging method for taking packages.io as the default installation.
2. Refactoring HTTP REST APIs to be compatible with EMQX.
3. Remove CXX compiler requirement
4. Rule engine now supports parsing JSON payloads.
5. Fix Nanolib's compatibility with GCC under 4.9 #634
6. Fix data racing of issue #666
7. Fix MQTT over Websocket # 668
8. Fix double free of Retain msg #689
9. Fix disconnect msg does not cleanup last will msg.