code: function(prepend, tileSize) {
          var grid = this.grid;
          var colIndex = prepend ? 0 : (grid[0].length - 1);
          var sign = prepend ? -1 : 1;
          var tileLayout = this.gridLayout;
          tileLayout.startcol += sign;
  
          for (var i=0, len=grid.length; i<len; i++) {
              var row = grid[i];
              var position = row[colIndex].position.clone();
              var tile = row[prepend ? 'pop' : 'shift']();            
              position.x += tileSize.w * sign;
              tile.moveTo(this.getTileBoundsForGridIndex(i, colIndex), position);
              row[prepend ? 'unshift' : 'push'](tile);
          }
      }
docs: Method: shiftColumn
  Shift grid work in the other dimension
  
  Parameters:
  prepend - {Boolean} if true, prepend to beginning.
  if false, then append to end
  tileSize - {Object} rendered tile size; object with w and h properties