Updating README

ashwanthkumar · ashwanthkumar · commit 8482b6688100 · 2015-05-22T08:34:22.000+05:30
diff --git a/README.md b/README.md
@@ -67,6 +67,7 @@ Available methods on `SlackAttachment`
 - `author`
 - `title`
 - `text`
+- `imageUrl`
 - `addField`
 
 ## License
