- Clean up unnecessary APIs in RetryHandler.
- Make sure follow redirect option is set correctly to NettyHttpClient
- General clean up and organizing.

- Created ribbon-http and ribbon-loadbalancer
- Removed httpasyncclient
- Refactor load balancer logic to make it based on Rx and decouple from Client APIs

Javadoc added. Set content-length when POST with raw ByteBuf. Added AutoRetainResponse property to auto retain ByteBuf in NettyHttpResponse when turned on.

Implemented redirect using Observable APIs. Added JUnit tests. Retrofit serialization framework to RestClient.

- Added ribbon-rxnetty module for asynchronous HTTP communication based on Netty and RxJava
- IClientConfig and IClientConfigKey supports typed property
- Updates to serialization factory and serializer interfaces (replaced Guava TypeToken with TypeDef in the interfaces)
- Updates to HttpRequest and HttpResponse interfaces with addition of HttpHeaders