When `RevealMarkdown.initialize` is called, it use `md.render` to render markdown, but no until we parse meta, the md.options.breaks would be default value we set in extra.js.

So this commit move forward the whole meta parsing block. Ensure line break setting changed before `md.render` get called.

Signed-off-by: Yukai Huang <yukaihuangtw@gmail.com>