chore: upgrade codecov

jestjs/jest#5352 (comment)

.travis.yml

@@ -1,8 +1,5 @@
 language: node_js
 
-before_install:
- - npm install -g [email protected]
-
 node_js:
  - "8"
  - "9"
@@ -11,4 +8,4 @@ node_js:
 
 script:
  - npm run validate
- - cat ./coverage/lcov.info | ./node_modules/codecov.io/bin/codecov.io.js
+ - npx codecov

README.md

@@ -17,7 +17,7 @@
 [![NPM Version](https://img.shields.io/npm/v/redux-form.svg?style=flat)](https://www.npmjs.com/package/redux-form)
 [![NPM Downloads](https://img.shields.io/npm/dm/redux-form.svg?style=flat)](https://npmcharts.com/compare/redux-form?minimal=true)
 [![Build Status](https://img.shields.io/travis/erikras/redux-form/v6.svg?style=flat)](https://travis-ci.org/erikras/redux-form)
-[![codecov.io](https://codecov.io/gh/erikras/redux-form/branch/master/graph/badge.svg)](https://codecov.io/gh/erikras/redux-form)
+[![codecov.io](https://codecov.io/gh/redux-form/redux-form/branch/master/graph/badge.svg)](https://codecov.io/gh/redux-form/redux-form)
 [![Code Climate](https://codeclimate.com/github/erikras/redux-form/badges/gpa.svg)](https://codeclimate.com/github/erikras/redux-form)
 [![styled with prettier](https://img.shields.io/badge/styled_with-prettier-ff69b4.svg)](https://github.com/prettier/prettier)
 [![PayPal donate button](http://img.shields.io/paypal/donate.png?color=yellowgreen)](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=3QQPTMLGV6GU2)