Attempt to add Coveralls

.travis.yml

@@ -1,3 +1,6 @@
 language: go
 go:
   - 1.14
+install: go get github.com/mattn/goveralls
+script:
+  - "$GOPATH/bin/goveralls -service=travis-ci"

README.md

@@ -2,7 +2,6 @@ ACE
 ========
 
 [![godoc badge](http://godoc.org/github.com/contentway/ace?status.svg)](http://godoc.org/github.com/contentway/ace)
-[![gocover badge](http://gocover.io/_badge/github.com/contentway/ace?t=3)](http://gocover.io/github.com/contentway/ace)
 [![Build Status](https://api.travis-ci.org/contentway/ace.svg?branch=master&t=3)](https://travis-ci.org/contentway/ace)
 [![Go Report Card](http://goreportcard.com/badge/contentway/ace?t=3)](http://goreportcard.com/report/contentway/ace)