Adding ActorMethodDispatcher that is responsible for the communication
between the ActorServer (Drb server) and the actors.
Began working on the API of ActorClient; expanded API of ActorServer.
ActorClient skeleton now extends Actor
Moving @receivers from actor_server to actor_method_dispatcher. Adding
to stop and check the drb server status.
Adding Concurrent::ActorServer#start method - that is responsible to create a new drb server instance if the current one isn't running.
wip: Began TDD of RemoteActor/ActorClient API
RemoteActor - Logging last connection error
Adding the #pool method to ActorServer.

Adding the #pool method to ActorServer so the actor server can creates a
pool of actors.

-----------------
Example:

class ActorA < Actor
end

class ActorB < Actor
end

class ActorC < Actor
end

actor_server = ActorServer.new('localhost', 8888)
mailbox_a = actor_server.pool('foo', ActorA) # defaults to 1
mailbox_b = actor_server.pool('bar', ActorB, 1)
mailbox_c = actor_server.pool('baz', ActorC, 5)

actor_server.run!
----------------

Bonus: Fixing the actor server specs - using the method #run! (from
Runable) instead of #start method (which doesn't exist anymore).
Adding more specs to ActorServer#pool.

The ActorServer#pool can receive the size of the actor pool as a
parameter - adding specs to cover it.
Adding supervisors to the Actors manage by the ActorServer.

Right now each actor pool has its own supervisor. But we might change it
to the ActorServer be the supervisor of all the actor's pool.
Sending the message to a specific actors pool.

---------

server = Concurrent::ActorServer.new
server.pool('foo', MyActor, 10)

server.post('foo', message) # sends the message to the 'foo' pool.
---------
Fixing remote actor specs.

The last commits changed how the ActorServer works and then we had
to update the remote actor specs with the new behaviour.
[RemoteActor] - More specs passing
[RemoteActor] - More specs passing[2]
Spike of remote actor/server and all actor #post method variants.
Merge latest branch 'master' from core repo into using-drb
Spiked a RemoteActorDrbProxy class that decouples RemoteActor from the underlying RMI library.
RemoteActorSpec:  WIP
Adding support to ActorServer#post!
Merge branch 'master' into jerry