Updated cocoapods instructions to point to 3.0.0-beta.3 to avoid confusion.

README.md

@@ -63,7 +63,7 @@ source 'https://github.com/CocoaPods/Specs.git'
 platform :ios, '8.0'
 use_frameworks!
 
-pod 'Alamofire', '~> 3.0'
+pod 'Alamofire', '~> 3.0.0-beta.3'
 ```
 
 Then, run the following command: