Remove broken hyperlink

README.md

@@ -249,9 +249,7 @@ These are the idiomatic ways for components to notify others about things:
 * __Callback blocks:__ _(one-to-one)_ Allow for a more loose coupling, while keeping related code sections close to each other. Also scales better than delegation when there are many senders.
 * __Notification Center:__ _(one-to-many)_ Possibly the most common way for objects to emit “events” to multiple observers. Very loose coupling — notifications can even be observed globally without reference to the dispatching object.
 * __Key-Value Observing (KVO):__ _(one-to-many)_ Does not require the observed object to explicitly “emit events” as long as it is _Key-Value Coding (KVC)_ compliant for the observed keys (properties). Usually not recommended due to its implicit nature and the cumbersome standard library API.
-* __Signals:__ _(one-to-many)_ The centerpiece of [ReactiveCocoa][reactivecocoa-github], they allow chaining and combining to your heart's content, thereby offering a way out of [callback hell][elm-escape-from-callback-hell].
-
-[elm-escape-from-callback-hell]: http://elm-lang.org/learn/escape-from-callback-hell
+* __Signals:__ _(one-to-many)_ The centerpiece of [ReactiveCocoa][reactivecocoa-github], they allow chaining and combining to your heart's content, thereby offering a way out of "callback hell".
 
 ### Models