Version 2.0.0

Faster than ever.
Added Promises/A+ implementation.
Added middleware support.
Added push support.
Added oneway call support.
Added idempotent calls automatically fail retry support.
Added asynchronous call support.
Added load balancing, and fail switch support.
Improved the client and server API.
Added socket client without extension.
Separated hprose-yii into a standalone project.
Separated hprose-symfony into a standalone project.
Separated hprose-swoole into a standalone project.