Different result parsedown vs original due to new line

[Snoozerworks]

Hi,
Noticed a difference between the original parser and parsedown.

This markdown fail because "## Last heading" is not converted

`## First heading
<ul><li>Hoo
<ul>
<li>Hoo</li>
</ul></li>
</ul>

## Last heading`

However, it works if adding a newline after the nested list like this 
`## First heading
<ul><li>Hoo
<ul>
<li>Hoo</li>
</ul>
</li>
</ul>

## Last heading`

Or removing the newline before the nested list, like this
`## First heading
<ul><li>Hoo<ul>
<li>Hoo</li>
</ul></li>
</ul>

## Last heading`

[aidantwoods]

This was fixed in #514 :)