Line-break tag noise added to multi-line HTML #157

Reproduction:

1. Take some multi-line HTML, such as the output from here: http://www.tablesgenerator.com/html_tables
2. Paste into an email and render. There will be a whole bunch of empty lines above the rendered table.
3. Do it again with a breakpoint at the rendered output. You'll see a bunch of <br> tags have been added.

The extra tags either shouldn't be there at all before being passed to marked.js, or should be stripped (by a custom renderer?).

(I don't have time to check right now, but I'm not entirely sure why they're there at all.)