Added test for #25. Looks to be working.

test/cases/github-style-linebreaks.html

@@ -0,0 +1,4 @@
+
+<pre><code>code can go here
+this is rendered on a second line
+</code></pre>

test/cases/github-style-linebreaks.md

@@ -0,0 +1,4 @@
+```
+code can go here
+this is rendered on a second line
+```