escaping of "<" breaks span-level html

tests/data/span_level_html.html

@@ -0,0 +1 @@
+<p>Here's an <b>important</b> <a href=''>link</a>.</p>

tests/data/span_level_html.md

@@ -0,0 +1 @@
+Here's an <b>important</b> <a href=''>link</a>.

tests/data/special_characters.html

@@ -4,5 +4,6 @@
 <p>4 &lt; 5 and 6 > 5.</p>
 <p>Here's a <a href="http://example.com/?foo=1&amp;bar=2">link</a> with an ampersand in the URL.</p>
 <p>Here's an inline <a href="/script?foo=1&amp;bar=2">link</a>.</p>
+<p><a href="http://example.com/autolink?a=1&amp;b=2">http://example.com/autolink?a=1&amp;b=2</a></p>
 <hr />
 <p>Based on <a href="http://daringfireball.net/projects/downloads/MarkdownTest_1.0.zip">the original</a> test suite.</p>

tests/data/special_characters.md

@@ -1,6 +1,6 @@
 AT&T has an ampersand in their name.
 
-AT&T is another way to write it.
+AT&T is another way to write it.
 
 This & that.
 
@@ -12,6 +12,8 @@ Here's an inline [link](/script?foo=1&bar=2).
 
 [1]: http://example.com/?foo=1&bar=2
 
+<http://example.com/autolink?a=1&b=2>
+
 ---
 
 Based on [the original](http://daringfireball.net/projects/downloads/MarkdownTest_1.0.zip) test suite.