Update README

Changed labels to master branch

Author: Aleffio

README.md

@@ -1,5 +1,5 @@
-[![Build Status](https://travis-ci.org/Adyen/adyen-python-api-library.svg?branch=develop)](https://travis-ci.org/Adyen/adyen-python-api-library)
-[![Coverage Status](https://coveralls.io/repos/github/Adyen/adyen-python-api-library/badge.svg?branch=develop)](https://coveralls.io/github/Adyen/adyen-python-api-library?branch=develop)
+[![Build Status](https://travis-ci.org/Adyen/adyen-python-api-library.svg?branch=master)](https://travis-ci.org/Adyen/adyen-python-api-library)
+[![Coverage Status](https://coveralls.io/repos/github/Adyen/adyen-python-api-library/badge.svg?branch=master)](https://coveralls.io/github/Adyen/adyen-python-api-library?branch=master)
 
 # Adyen APIs Library for Python