add a link to opencollective

README.md

@@ -1,4 +1,4 @@
-# Android Orma [![Circle CI](https://circleci.com/gh/maskarade/Android-Orma/tree/master.svg?style=svg)](https://circleci.com/gh/maskarade/Android-Orma/tree/master) [ ![Download](https://api.bintray.com/packages/orma/maven/orma/images/download.svg) ](https://bintray.com/orma/maven/orma/) [![Gitter](http://badges.gitter.im/Android-Orma.svg)](https://gitter.im/Android-Orma/Lobby)
+# Android Orma [![Circle CI](https://circleci.com/gh/maskarade/Android-Orma/tree/master.svg?style=svg)](https://circleci.com/gh/maskarade/Android-Orma/tree/master) [ ![Download](https://api.bintray.com/packages/orma/maven/orma/images/download.svg) ](https://bintray.com/orma/maven/orma/) [![Gitter](http://badges.gitter.im/Android-Orma.svg)](https://gitter.im/Android-Orma/Lobby) ![backers](https://opencollective.com/android-orma/tiers/backer/badge.svg?label=backer&color=brightgreen)
 
 <p align="center">
 <img src="Orma.png" width="256" height="256"  alt="Android Orma" />
@@ -1282,6 +1282,8 @@ FUJI Goro ([gfx](https://github.com/gfx)).
 
 And contributors are listed here: [Contributors](https://github.com/gfx/Android-Orma/graphs/contributors)
 
+If you are interested in sponsoring this project, it is really welcome, as I'll spend more time to develop this software: https://opencollective.com/android-orma
+
 ## License
 
 Copyright (c) 2015 FUJI Goro (gfx).