Add coverage badge

.travis.yml

@@ -5,13 +5,16 @@ env:
 
 install:
   - go get golang.org/x/lint/golint
+  - go get golang.org/x/tools/cmd/cover
+  - go get github.com/mattn/goveralls
 
 script:
   - go build ./...
   - go test -v ./...
-  - go test -cover -race ./...
   - go vet ./...
   - test -z "$(gofmt -d -s *.go)"
   - golint ./...
+  - go test -v -covermode=count -coverprofile=coverage.out
+  - goveralls -coverprofile=coverage.out -service=travis-ci -repotoken $COVERALLS_TOKEN
 
 sudo: false

README.md

@@ -3,6 +3,7 @@
 [![Build Status](https://travis-ci.org/twpayne/go-polyline.svg?branch=master)](https://travis-ci.org/twpayne/go-polyline)
 [![GoDoc](https://godoc.org/github.com/twpayne/go-polyline?status.svg)](https://godoc.org/github.com/twpayne/go-polyline)
 [![Report Card](https://goreportcard.com/badge/github.com/twpayne/go-polyline)](https://goreportcard.com/report/github.com/twpayne/go-polyline)
+[![Coverage Status](https://coveralls.io/repos/github/twpayne/go-polyline/badge.svg)](https://coveralls.io/github/twpayne/go-polyline)
 
 Package `polyline` implements a Google Maps Encoding Polyline encoder and decoder.