Blockquotes & HR

Blockquotes:

> This is a quote.
> Spans multiple lines.

> Different quote.

Becomes:

<blockquote>
<p>This is a quote.
Spans multiple lines.</p>
</blockquote>
<blockquote>
<p>Different quote.</p>
</blockquote>

Nested:

> Outer
>> Inner

Horizontal rule (any of):

---
***
___
- - -

Becomes <hr /> (or <hr> in HTML5).

Three or more of the SAME char (with optional spaces between).

Note: -- (just two dashes) is NOT a horizontal rule — could be confused with em-dash text.