Add a custom error page

Author: edunham

error.html

@@ -0,0 +1,15 @@
+---
+layout: default
+title: Error 
+---
+<div align="center">
+<br>
+<img src="logos/error.png">
+<br>
+<br>
+    <p>Something went terribly wrong!</p>
+    <p>I was just minding my own business and now I'm over here on an error
+    page!</p>
+    <p>Can you <a href="https://github.com/rust-lang/rust-www">help make this
+        site better</a>?</p>
+</div>