Fix license badge

Author: eriwen

README.md

@@ -1,7 +1,7 @@
 stackframe 
 ==========
 ## JS Object representation of a stack frame
-[![Build Status](https://travis-ci.org/stacktracejs/stackframe.svg?branch=master)](https://travis-ci.org/stacktracejs/stackframe) [![Coverage Status](https://img.shields.io/coveralls/stacktracejs/stackframe.svg)](https://coveralls.io/r/stacktracejs/stackframe?branch=master) [![GitHub license](https://img.shields.io/github/license/stacktracejs/stackframe.svg)](https://opensource.org/licenses/MITx)
+[![Build Status](https://travis-ci.org/stacktracejs/stackframe.svg?branch=master)](https://travis-ci.org/stacktracejs/stackframe) [![Coverage Status](https://img.shields.io/coveralls/stacktracejs/stackframe.svg)](https://coveralls.io/r/stacktracejs/stackframe?branch=master) [![GitHub license](https://img.shields.io/github/license/stacktracejs/stackframe.svg)](https://opensource.org/licenses/MIT)
 
 Underlies functionality of other modules within [stacktrace.js](https://www.stacktracejs.com).