Fix broken link in readme (#21)

diff --git a/README.md b/README.md
index 2bba63e..a6951f0 100644
--- a/README.md
+++ b/README.md
@@ -57,4 +57,4 @@
 The Dart language doesn't have character literals.
 If that ever changes, this package will become irrelevant.
 Until then, this package can be used for the most common characters.
-See [http://dartbug.com/4415](request for character literals).
+See [request for character literals](http://dartbug.com/4415).