Remove 'fowardable' module from Robot

This module was no longer in use by the class, and thus
was removed.
Reword robot.with_placement()
Adjust whitespace in ToyRobot::Factory
Reword pose.update!() to use += operator
Simplify RobotController, remove Command::Token dependancy

RobotController now responds to messages with the following
format: robot_controller.<token>(<args>)

ToyRobot::Application updated to use this pattern when
messaging the controller.