Response implementation. When Runnbale is executed, it just hands the
request to Fiber and returns. When the Fiber finishes the execution, it sets
response in the
FutureTask
ResponseImpl executes things synchronously and waits for the return
parameter.
author: Jitendra Kotamraju
Parameters: runnable - This Runnable is executed asynchronously. Parameters: handler - Optional AsyncHandler to invoke at the endof the processing. Can be null.