README: CI on master branch, not on next branch

Author: aquynh

README.md

@@ -1,8 +1,8 @@
 Capstone Engine
 ===============
 
-[![Build Status](https://travis-ci.org/aquynh/capstone.svg?branch=next)](https://travis-ci.org/aquynh/capstone)
-[![Build status](https://ci.appveyor.com/api/projects/status/a4wvbn89wu3pinas/branch/next?svg=true)](https://ci.appveyor.com/project/aquynh/capstone/branch/next)
+[![Build Status](https://travis-ci.org/aquynh/capstone.svg?branch=master)](https://travis-ci.org/aquynh/capstone)
+[![Build status](https://ci.appveyor.com/api/projects/status/a4wvbn89wu3pinas/branch/master?svg=true)](https://ci.appveyor.com/project/aquynh/capstone/branch/master)
 
 Capstone is a disassembly framework with the target of becoming the ultimate
 disasm engine for binary analysis and reversing in the security community.