code: function(currentDirection){
              var directions = ['up', 'right', 'down', 'left'],
                  currentDirIndex = directions.indexOf(currentDirection),
                  newDirIndex;
              // if currentDirection is not valid or is the last in the array use the first direction in the array
              if(currentDirIndex === -1 || currentDirIndex === directions.length - 1){
                  newDirIndex = 0;
              } else {
                  newDirIndex = currentDirIndex + 1;
              }
              return directions[newDirIndex];
          }
docs: Gets the next direction in the list
  @method getNextDirection
  @param {String} direction - The current direction.
  @return {String}