Switched `Build Status` badge over to only report on the `master` branch.

README.md

@@ -1,6 +1,6 @@
 ![Alamofire: Elegant Networking in Swift](https://raw.githubusercontent.com/Alamofire/Alamofire/assets/alamofire.png)
 
-[![Build Status](https://travis-ci.org/Alamofire/Alamofire.svg)](https://travis-ci.org/Alamofire/Alamofire)
+[![Build Status](https://travis-ci.org/Alamofire/Alamofire.svg?branch=master)](https://travis-ci.org/Alamofire/Alamofire)
 [![CocoaPods Compatible](https://img.shields.io/cocoapods/v/Alamofire.svg)](https://img.shields.io/cocoapods/v/Alamofire.svg)
 [![Carthage Compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage)
 [![Platform](https://img.shields.io/cocoapods/p/Alamofire.svg?style=flat)](http://cocoadocs.org/docsets/Alamofire)