take coverage

.travis.yml

@@ -3,5 +3,8 @@ go: 1.x
 os:
   - linux
   - osx
+before_install:
+  - go get github.com/mattn/goveralls
 script:
   - go test ./...
+  - goveralls -service=travis-ci

README.md

@@ -1,6 +1,7 @@
 :x: loc
 =======
 [![Build Status][build badge]][travis result]
+[![Coverage Status][coverage status]][coverage result]
 
 [loc][loc document] is a small library to make a nice-looking error with source location information.
 It provides a struct to represent a source file, a specific position in code and an error related to
@@ -97,3 +98,5 @@ Please see [documentation][loc document] to know whole APIs.
 [loc document]: https://godoc.org/github.com/rhysd/loc
 [build badge]: https://travis-ci.org/rhysd/loc.svg?branch=master
 [travis result]: https://travis-ci.org/rhysd/loc
+[coverage status]: https://coveralls.io/repos/github/rhysd/loc/badge.svg?branch=master
+[coverage result]: https://coveralls.io/github/rhysd/loc?branch=master