Allow comma-separated paths for --tags.

        opts.separator "Tweaking:"

        opts.separator ""

        opts.on('--tags=PATH',

          "Path to custom tag implementations.",

        opts.on('--tags=PATH1,PATH2', Array,

          "Paths to custom tag implementations.",

          "",

          "Can be a path to single Ruby file or a directory.",

          "Paths can point to specific Ruby files or to a directory,",

          "in which case all ruby files in that directory are loaded.",

          "",

          "This option can be used repeatedly to include multiple",

          "tags from different places.",

          "",

          "See also: https://github.com/senchalabs/jsduck/wiki/Custom-tags") do |path|

          @custom_tag_paths << canonical(path)

          "See also: https://github.com/senchalabs/jsduck/wiki/Custom-tags") do |paths|

          @custom_tag_paths += paths.map {|p| canonical(p) }

        end

        opts.on('--ignore-global',