def size=(size)
      unless size.nil?
        case size
        when String
          width, height = size.split('x')
        when Array
          width, height = size
        when Hash
          width = size[:width]
          height = size[:height]
        else
          raise "Don't know how to set size from #{size.class}!"
        end

        self.width = width if width
        self.height = height if height
      end
    end
def size=(size)
      unless size.nil?
        case size
        when String
          width, height = size.split('x')
        when Array
          width, height = size
        when Hash
          width = size[:width]
          height = size[:height]
        else
          raise "Don't know how to set size from #{size.class}!"
        end

        self.width = width if width
        self.height = height if height
      end
    end
Sets the size of the map

 <tt>size</tt>::   Can be a "wxh", [w,h] or {:width => x, :height => y}