update readme

README.md

 # Bokeh Portal Library
 
-## Documentation
+## Learn
 
 * User documentation can be read on [the official Wiki](http://wiki.bokeh-library-portal.org/)
 * [User friendly changelog](VERSIONS)
 * [Developer changelog](VERSIONS_DEV.md)
 
 
-## Installation
+## Install
 
 See [english](INSTALL.en.md) or [french](INSTALL.fr.md) documentation.
 
+## Develop
 
-## LICENSE
+See [How to contribute](http://git.afi-sa.fr/afi/opacce/blob/master/CONTRIB.en.md) or [comment contribuer](http://git.afi-sa.fr/afi/opacce/blob/master/CONTRIB.fr.md)
+
+## License
 
 BOKEH is released under a dual-license AGPL / Proprietary use.