def compress(id, &block)
      if block
        compressors[id] << block
      else
        compressors[id] << Proc.new {}
      end
    end
def compress(id, &block)
      if block
        compressors[id] << block
      else
        compressors[id] << Proc.new {}
      end
    end
Add or override a customization for the compressor with the given +id+.
 When given multiple blocks with the same +id+, they are evaluated
 _in order_, so the last block evaluated will take precedence over the
 previous ones.

 @example With customization
   compress :dmg do
     window_bounds '10, 20, 30, 40'
   end

 @example Without customization
   compress :tgz

 If multiple +compress+ blocks are specified, the "most prefered" one for
 the current system will be used.

 @param [Symbol] id
   the id of the compressor to customize