Simplify Contributions section in readmes

PUBLISHED_FROM=3a14579dabba4088e54350945dc17fd6ebb0d700

README.md

@@ -182,18 +182,16 @@ are appended to the output buffer as-is
 
 # Contributions
 
-People who have agreed to the
-[Cesanta CLA](http://cesanta.com/contributors_la.html)
-can make contributions. Note that the CLA isn't a copyright
-_assigment_ but rather a copyright _license_.
-You retain the copyright on your contributions.
+To submit contributions, sign
+[Cesanta CLA](https://docs.cesanta.com/contributors_la.shtml)
+and send GitHub pull request. You retain the copyright on your contributions.
 
 # Licensing
 
-Frozen is released under commercial and [GNU GPL v.2](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html) open source licenses. 
+Frozen is released under commercial and [GNU GPL v.2](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html) open source licenses.
 
-Commercial Projects: 
-Once your project becomes commercialised GPLv2 licensing dictates that you need to either open your source fully or purchase a commercial license. Cesanta offer full, royalty-free commercial licenses without any GPL restrictions. If your needs require a custom license, we’d be happy to work on a solution with you. [Contact us for pricing.] (https://www.cesanta.com/contact) 
+Commercial Projects:
+Once your project becomes commercialised GPLv2 licensing dictates that you need to either open your source fully or purchase a commercial license. Cesanta offer full, royalty-free commercial licenses without any GPL restrictions. If your needs require a custom license, we’d be happy to work on a solution with you. [Contact us for pricing.] (https://www.cesanta.com/contact)
 
-Prototyping: 
-While your project is still in prototyping stage and not for sale, you can use Frozen’s open source code without license restrictions. 
+Prototyping:
+While your project is still in prototyping stage and not for sale, you can use Frozen’s open source code without license restrictions.