Added convenience method to add a single object with ContentTransformer to the HttpClientRequest.
Fixes issue #134

Provided overloads for all method taking requestIdHeaderName to use the default header name.
The default header name can be set by calling RxContexts.useRequestIdContextKey()
Merge branch 'master' of github.com:Netflix/RxNetty
Merge pull request #135 from allenxwang/master

Added convenience method to add a single object with ContentTransformer to the HttpClientRequest
Fix test failure

This test was dependent on the mock server NOT closing the connection on receive but was not setting that state on the server handler.
In some cases, when this state was left uncleared from another test & the connection close from server happens fast enough, the test will fail.

Now, clearing up the state in teardown()
Merge pull request #136 from NiteshKant/master

Fixes issue #134
Merge branch 'master' of https://github.com/Netflix/RxNetty into metrics
WIP commit for Metrics (issue #98)

Did a few changes in the design as discussed in the github issue.

This code change suffices for the current Pool State change events. I will be adding the remaining events and migrate the tests to use the new model.