README: add instructions to build Amber with Grunt.js

README.md

@@ -24,6 +24,16 @@ License
 
 Amber is released under the MIT license. All contributions made for inclusion are considered to be under MIT.
 
+Building Amber
+--------------
+
+Since 0.10.0 Amber uses [Grunt.js](http://gruntjs.com/) as build system.
+To compile Amber on the commandline execute the following commands:
+
+#    cd ${Amber_DIR}
+#    npm install
+#    ./node_modules/grunt/bin/grunt
+
 More infos
 ----------