Create renderer_data and pass it to callbacks
Add `render_inline` parameter to header and footer callbacks
Update HTML renderer to use new API
Put HTML callbacks at the end of their categories
Rename `raw_html_tag` to just `raw_html`
Call it `content` when it's rendered output, `text` otherwise

If it's rendered output, i.e. output coming from other callbacks,
it must be called `content`, and be the first parameter after `ob`.
Split `table` in `table_header` and `table_body`

Only one parameter  (`content`) can have rendered output.
The `table` callback contradicts this rule, so it has to be split
in `table_header` and `table_body`.

This also helps keep the HTML renderer code dry and readable.
Properly name category
Revert `hoedown_inline`
Merge pull request #124 from jmendeth/renderer-api

Renderer API