WIP: Restrict the set of allowed tags

[philschatz]

Current list:

a abbr blockquote br cite code dd dfn dl dt kbd li mark ol p pre q s
        samp small strike sub sup time ul var
address article aside bdi bdo body caption col colgroup data del div
        figcaption figure footer h1 h2 h3 h4 h5 h6 head header hgroup hr html
        img ins main nav rp rt ruby section span style summary sup table tbody
        td tfoot th thead title tr wbr

I'd say disallow br, meta, cite, dfn dl, dt, dd, kbd, mark, pre, s, samp, small, strike, time, var, address, article, aside, bdi, bdo, body, colgroup, data, del, div (maybe???), footer, h1, h2, h3, h4, h5, h6, head, hgroup, hr, html, ins, main, nav, rp, rt, ruby, summary, wbr (maybe more? I just glanced through dante's list) and b, i, u

[Dantemss]

I think we need to allow div for block math.
What about u? Don't think there's an alternative?

[philschatz]

Agreed that there may be no alternative to u but I'm not sure it needs to be available.