Docs: Add backers and sponsors from OpenCollective (#1705)

Your open collective backers & sponsors will show up on your readme automatically.  Also added badges on top.

README.md

@@ -5,7 +5,9 @@
   <p align="center">The streaming build system</p>
 </p>
 
-[![NPM version][npm-image]][npm-url] [![Downloads][downloads-image]][npm-url] [![Build Status][travis-image]][travis-url] [![Coveralls Status][coveralls-image]][coveralls-url] [![Gitter chat][gitter-image]][gitter-url]
+[![NPM version][npm-image]][npm-url] [![Downloads][downloads-image]][npm-url] [![Build Status][travis-image]][travis-url] [![Coveralls Status][coveralls-image]][coveralls-url] [![Gitter chat][gitter-image]][gitter-url] [![OpenCollective](https://opencollective.com/gulpjs/backers/badge.svg)](#backers)
+[![OpenCollective](https://opencollective.com/gulpjs/sponsors/badge.svg)](#sponsors)
+
 
 ## What is gulp?
 
@@ -89,6 +91,18 @@ We recommend these plugins:
 
 Anyone can help make this project better - check out our [Contributing guide](/CONTRIBUTING.md)!
 
+## Backers
+
+Support us with a monthly donation and help us continue our activities.
+
+![Backers][backers-image] [![Become a Backer][become-backer-image]][become-backer-url]
+
+## Sponsors
+
+Become a sponsor to get your logo on our README on Github.
+
+![Sponsors][sponsors-image] [![Become a Sponsor][become-sponsor-image]][become-sponsor-url]
+
 [downloads-image]: https://img.shields.io/npm/dm/gulp.svg
 [npm-url]: https://www.npmjs.com/package/gulp
 [npm-image]: https://img.shields.io/npm/v/gulp.svg
@@ -101,3 +115,10 @@ Anyone can help make this project better - check out our [Contributing guide](/C
 
 [gitter-url]: https://gitter.im/gulpjs/gulp
 [gitter-image]: https://badges.gitter.im/gulpjs/gulp.svg
+
+[backers-image]: https://opencollective.com/gulpjs/backers.svg
+[become-backer-url]: https://opencollective.com/gulpjs#backer
+[become-backer-image]: https://opencollective.com/static/images/become_backer.svg
+[sponsors-image]: https://opencollective.com/gulpjs/sponsors.svg
+[become-sponsor-url]: https://opencollective.com/gulpjs#sponsor
+[become-sponsor-image]: https://opencollective.com/static/images/become_sponsor.svg