README: Use the master branch in CI status badges

Author: elprans

README.md

@@ -1,5 +1,5 @@
-[![Build Status](https://travis-ci.org/Azure/azure-functions-python-worker.svg?branch=dev)](https://travis-ci.org/Azure/azure-functions-python-worker)
-[![Build status](https://ci.appveyor.com/api/projects/status/github/azure/azure-functions-python-worker?svg=true&branch=dev)](https://ci.appveyor.com/project/appsvc/azure-functions-python-worker)
+[![Build Status](https://travis-ci.org/Azure/azure-functions-python-worker.svg?branch=master)](https://travis-ci.org/Azure/azure-functions-python-worker)
+[![Build status](https://ci.appveyor.com/api/projects/status/github/azure/azure-functions-python-worker?svg=true&branch=master)](https://ci.appveyor.com/project/appsvc/azure-functions-python-worker)
 
 This repository will host the Python language worker implementation for Azure Functions. We'll also be using it to track work items related to Python support. Please feel free to leave comments about any of the features and design patterns.