add contributing section to the readme

Readme.md

@@ -102,3 +102,19 @@ To run the tests call:
 
     node lib/ace/test/all.js
 
+Contributing
+------------
+
+Ace wouldn't be where it is now without contributions. Feel free to fork and improve/enhance Ace in any way your want. If you feel that the editor and whole Ace community benefits from your changes feel free to open a pull request. To protect the interests of the Ace contributers and users we require contributers to sign a Contributers License Agreement (CLA) before we pull the changes into the main repository. Our CLA is the simplest of agreements, requiring that the contributions you make to an ajax.org project are only those you're allowed to make. This helps us significantly reduce future legal risk for everyone involved. It is easy, helps everyone, and is an easy ten minute one-time process for individuals. There are two versions of the agreement:
+
+1. [The Individual CLA](https://github.com/ajaxorg/ace/raw/master/doc/Contributor_License_Agreement-v2.pdf): use this version if you're working on an ajax.org in your spare time, or can clearly claim ownership of copyright in what you'll be submitting.
+2. [The Corporate CLA](https://github.com/ajaxorg/ace/raw/master/doc/Corporate_Contributor_License_Agreement-v2.pdf): have your corporate lawyer review and submit this if your company is going to be contributing to ajax.org  projects
+
+If you want to contribute to an ajax.org project please print the CLA and fill it out and sign it. Then either send it by snail mail or fax to us or send it back scanned (or as a photo) by email.
+
+Email: fabian.jakobs@web.de
+Fax: +31 (0) 206388953
+Address: Ajax.org B.V.
+  Keizersgracht 241
+  1016 EA, Amsterdam
+  the Netherlands