Improve Tag#parse documentation.

    attr_reader :multiline

    # Called by DocParser when the @tag is reached to do the parsing

    # from that point forward.  Gets passed an instance of DocParser.

    # from that point forward.  Gets passed an instance of DocScanner.

    #

    # Can return a hash or array of hashes representing the detected

    # @tag data.  Each returned hash must contain the :tagname key,

    # e.g.:

    #

    #     {:tagname => :protected, :foo => "blah"}

    #

    # All hashes with the same :tagname will later be combined

    # together and passed on to #process_doc method of this Tag class

    # that has @key field set to that tagname.

    def parse(p)

    end