ci: use github action, add badge

Author: danivek

.github/workflows/test.yml renamed to .github/workflows/build.yml

@@ -1,4 +1,4 @@
-name: test
+name: build
 
 on:
   push:

README.md

@@ -1,6 +1,6 @@
 # json-api-serializer
 
-[![Build Status](https://travis-ci.org/danivek/json-api-serializer.svg?branch=master)](https://travis-ci.org/danivek/json-api-serializer)
+[![build](https://github.com/danivek/json-api-serializer/workflows/build/badge.svg)](https://github.com/danivek/json-api-serializer/actions?query=workflow%3Abuild)
 [![Coverage Status](https://coveralls.io/repos/github/danivek/json-api-serializer/badge.svg?branch=master)](https://coveralls.io/github/danivek/json-api-serializer?branch=master)
 [![npm](https://img.shields.io/npm/v/json-api-serializer.svg)](https://www.npmjs.org/package/json-api-serializer)