README: add ismaintained.com badges

README.md

@@ -1,5 +1,10 @@
-Amber [![Gitter](https://badges.gitter.im/Join Chat.svg)](https://gitter.im/amber-smalltalk/amber?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![Travis CI Status](https://secure.travis-ci.org/amber-smalltalk/amber.png)](https://travis-ci.org/#!/amber-smalltalk/amber) [![devDependency status](https://david-dm.org/amber-smalltalk/amber/dev-status.svg?style=flat)](https://david-dm.org/amber-smalltalk/amber#info=devDependencies) [![Bountysource](https://www.bountysource.com/badge/team?team_id=19271&style=raised)](https://www.bountysource.com/teams/amber-smalltalk?utm_source=amber-smalltalk&utm_medium=shield&utm_campaign=raised)
-=====
+Amber
+====
+
+[![Gitter](https://badges.gitter.im/Join Chat.svg)](https://gitter.im/amber-smalltalk/amber?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![Average time to resolve an issue](http://isitmaintained.com/badge/resolution/amber-smalltalk/amber.svg)](http://isitmaintained.com/project/amber-smalltalk/amber "Average time to resolve an issue")
+[![Percentage of issues still open](http://isitmaintained.com/badge/open/amber-smalltalk/amber.svg)](http://isitmaintained.com/project/amber-smalltalk/amber "Percentage of issues still open")
+
+[![Travis CI Status](https://secure.travis-ci.org/amber-smalltalk/amber.png)](https://travis-ci.org/#!/amber-smalltalk/amber) [![devDependency status](https://david-dm.org/amber-smalltalk/amber/dev-status.svg?style=flat)](https://david-dm.org/amber-smalltalk/amber#info=devDependencies) [![Bountysource](https://www.bountysource.com/badge/team?team_id=19271&style=raised)](https://www.bountysource.com/teams/amber-smalltalk?utm_source=amber-smalltalk&utm_medium=shield&utm_campaign=raised)
 
 
 By Nicolas Petton <petton.nicolas@gmail.com> and [Amber contributors](https://github.com/amber-smalltalk/amber/contributors)