Underlined Headers

[Olllom]

This is a minor one.

I noticed that when I have underlined titles in a notebook's markdown cell the number signs appear in the toc.

For example,

## Some Title
---

gives

• ## Some Title

rather than

• Some Title

[mgeier]

Why would you write such a thing?
That doesn't make any sense.

Different Markdown parsers behave differently in this case: http://johnmacfarlane.net/babelmark2/?normalize=1&text=%23%23+Some+Title%0A---
But none of those gives the result you were expecting.

nbsphinx currently uses pandoc, but with #36 we probably switch to a CommonMark-compatible parser.
Either way, that doesn't change that the input is strange.