Use master branch for badge

README.md

@@ -3,7 +3,7 @@
 </p>
 
 <p align="center">
-<a href="https://circleci.com/gh/onevcat/Kingfisher"><img src="https://img.shields.io/circleci/project/onevcat/Kingfisher.svg"></a> 
+<a href="https://circleci.com/gh/onevcat/Kingfisher"><img src="https://img.shields.io/circleci/project/onevcat/Kingfisher/master.svg"></a> 
 <a href="https://github.com/Carthage/Carthage/"><img src="https://img.shields.io/badge/Carthage-✔-f2a77e.svg?style=flat"></a> 
 <a href="http://cocoadocs.org/docsets/Kingfisher"><img src="https://img.shields.io/cocoapods/v/Kingfisher.svg?style=flat"></a> 
 <a href="https://raw.githubusercontent.com/onevcat/Kingfisher/master/LICENSE"><img src="https://img.shields.io/cocoapods/l/Kingfisher.svg?style=flat"></a>