added gfm table support #2
added gfm table support #2

To activate it:
    $ciconia->addExtension(new \Ciconia\Extension\Gfm\TableExtension());

kzykhys/Ciconia,scribenet/jabiru,fluxbb/commonmark,scribenet/Scrible,gharlan/Ciconia,scribenet/jabiru,scribenet/Scrible,simonfork/Ciconia