Update Travis badge URL to reflect master's status

Author: Rishabh Karnad

README.md

@@ -2,7 +2,7 @@
 
 [![Backers on Open Collective](https://opencollective.com/vue-native-core/backers/badge.svg)](#backers)
 [![Sponsors on Open Collective](https://opencollective.com/vue-native-core/sponsors/badge.svg)](#sponsors)
-[![Build Status](https://travis-ci.com/GeekyAnts/vue-native-core.svg?branch=develop)](https://travis-ci.com/GeekyAnts/vue-native-core)
+[![Build Status](https://travis-ci.com/GeekyAnts/vue-native-core.svg?branch=master)](https://travis-ci.com/GeekyAnts/vue-native-core)
 
 Visit our website at [vue-native.io](https://vue-native.io) or read the official documentation [here](https://vue-native.io/docs/installation.html).