Add example site.

* .gitignore: Ignore example build artifacts.
* example/haunt.scm: New file.
* example/posts/foo.sxml: New file.
* example/posts/bar.html: New file.

example/posts/bar.html

@@ -0,0 +1,8 @@
+title: A Foo Walks Into a Bar
+date: 2015-04-11 20:00
+tags: bar
+---
+<p>
+  This is an example using raw HTML, because Guile doesn't have a
+  Markdown parser.
+</p>