Validate MOVE command

Update processCommand test to validate MOVE command to make sure MOVE
command will not cause the robot to fall off the table
Added Direction and Robot test and class

Direction class for process turn and move
Robot class for storing x, y and face values
Update Direction tests

update turnLeft and turnRight tests to check for unknown current
direction
Fix Direction module

return the current direction when direction is unknown
Update RobotController implementation

* added left, right, move implementation
* refactor tests
Added Table tests

* moved validate x and y position tests into table_spec
* added skeleton table class
Update Table implementation

* added validate(x,y) method
* refactor Table test