Refactor to use codecov instead of coveralls

Author: wooorm

.travis.yml

@@ -6,4 +6,4 @@ node_js:
 - '0.12'
 - iojs
 sudo: false
-after_script: npm install [email protected] && cat ./coverage/lcov.info | coveralls
+after_script: npm install codecov.io && cat ./coverage/lcov.info | codecov

readme.md

@@ -1,4 +1,4 @@
-# mdast-validate-links [![Build Status](https://img.shields.io/travis/wooorm/mdast-validate-links.svg?style=flat)](https://travis-ci.org/wooorm/mdast-validate-links) [![Coverage Status](https://img.shields.io/coveralls/wooorm/mdast-validate-links.svg?style=flat)](https://coveralls.io/r/wooorm/mdast-validate-links?branch=master)
+# mdast-validate-links [![Build Status](https://img.shields.io/travis/wooorm/mdast-validate-links.svg)](https://travis-ci.org/wooorm/mdast-validate-links) [![Coverage Status](https://img.shields.io/codecov/c/github/wooorm/mdast-validate-links.svg)](https://codecov.io/github/wooorm/mdast-validate-links)
 
 [**mdast**](https://github.com/wooorm/mdast) plug-in to validate if links to
 headings and files in markdown point to existing things.