Pass Request type not to use timeout
Pass callback to Actor instead of using Future

`ask` does not allow infinite timeout length.
(https://groups.google.com/forum/#!topic/akka-user/fWxZ5-gCEBA and https://www.assembla.com/spaces/akka/tickets/1883)

To remove timeout specification, actor should be used with `tell` style.
In this case, there is no problem to process callback on actor's thread.
Therefore it is changed to use Request object to contain success and failure callbacks, and the operation target.

This fixes #3.
Fix #3 by removing actor timeout