Merge pull request #101 from twokul/promise#fail

adding promise#fail

README.md

@@ -136,6 +136,17 @@ getJSON("/post/1.json").then(function(post) {
 });
 ```
 
+You can also use `fail` for error handling, which is a shortcut for
+`then(null, rejection)`, like so:
+
+```javascript
+getJSON("/post/1.json").then(function(post) {
+  return getJSON(post.commentURL);
+}).fail(function(error) {
+  // handle errors
+});
+```
+
 ## Arrays of promises
 
 Sometimes you might want to work with many promises at once. If you

lib/rsvp/promise.js

@@ -120,6 +120,10 @@ Promise.prototype = {
     });
 
     return thenPromise;
+  },
+
+  fail: function(fail) {
+    return this.then(null, fail);
   }
 };