update: add badages and travis tests

Author: changkun

.travis.yml

@@ -0,0 +1,7 @@
+language: go
+
+script:
+  - make tests
+
+after_success:
+  - bash <(curl -s https://codecov.io/bash)

README.md

@@ -1,5 +1,8 @@
 # lockfree
 
+[![GoDoc](https://godoc.org/github.com/changkun/lockfree?status.svg)](https://godoc.org/github.com/changkun/lockfree)
+[![Build Status](https://travis-ci.org/changkun/lockfree.svg?branch=master)](https://travis-ci.org/changkun/lockfree) [![Go Report Card](https://goreportcard.com/badge/github.com/changkun/lockfree)](https://goreportcard.com/report/github.com/changkun/lockfree) [![codecov](https://codecov.io/gh/changkun/lockfree/branch/master/graph/badge.svg)](https://codecov.io/gh/changkun/lockfree) [![](https://img.shields.io/github/release/changkun/lockfree/all.svg)](https://github.com/changkun/lockfree/releases)
+
 Package lockfree offers lock-free utilities in Go.
 
 ## Contributing