Fixed the output of timecode blocks

Timecode blocks now generate a better HTML+RDFa for indexing.

The following wiki syntax

    00:00:00 --> 00:00:10

    inner content

produces the following HTML

    <section typeof="aa:annotation" data-begin="00:00:00" data-end="00:00:10">
      <span property="aa:begin">00:00:00</span> → <span property="aa:end">00:00:10</span>
      <div property="aa:content">
        <p>inner content</p>
      </div>
    </section>

which is serialized as (in turtle format):

    @prefix aa: <http://activearchives.org/terms/> .

    []
        aa:begin "00:00:00" ;
        aa:content "inner content" ;
        aa:end "00:00:10" ;
        a aa:annotation .