fix write yourself a scheme link

tuvtran · tuvtran · commit c259249a40e6 · 2017-04-28T01:35:23.000-04:00
diff --git a/README.md b/README.md
@@ -53,7 +53,7 @@ To get started, simply fork this repo. Please refer to [CONTRIBUTING.md](CONTRIB
 
 ## Haskell:
 * [Write You a Haskell - Build a modern functional compiler](http://dev.stephendiehl.com/fun/)
-* [Write Yourself a Scheme in 48 hours]()
+* [Write Yourself a Scheme in 48 hours](https://en.wikibooks.org/wiki/Write_Yourself_a_Scheme_in_48_Hours)
 
 ## Rust:
 * A Simple Web App in Rust
