Provide access to netty's ChannelHandlerContext to EgressRequest and IngressRequest.

When RxNetty provides a way to get ChannelHandlerContext from HttpServerRequest (Issue 214: https://github.com/ReactiveX/RxNetty/issues/214) we will only need this in EgressRequest.
Merge pull request #39 from NiteshKant/2.x

Provide access to netty's ChannelHandlerContext to EgressRequest and Ing...
Added EgressRequest.getIpAddress and getParameter.

* Also cleaned up FilterProcessor to use single() to prevent misbehaving filters