Fix paragraph breaking condition

[tanakahisateru]

Quote, HR and HTML are independent blocks even if not placed empty lines before them.

For example:

paragraph
> quote

paragraph
- - -

paragraph
<div>html block</div>

I expected to:

<p>paragraph</p>
<blockquote>
<p>quote</p>
</blockquote>
<p>paragraph</p>
<hr />
<p>paragraph</p>
<div>html block</div>

But actual:

<p>paragraph
&gt; quote</p>
<p>paragraph
- - -</p>
<p>paragraph
<div>html block</div></p>

Though even traditional markdown (https://daringfireball.net/projects/markdown/dingus) converts dense list block:

paragraph
- 1
- 2

to

<p>paragraph
- 1
- 2</p>

It is list specific behavior, but other blocks can be independent.