The User Guide is written in asciidoc and the source is published right in this wiki. So, you can edit the documentation right on master, see the Readme for more detail on this. The Asciidoc cheat-sheet is a nice place to start learning about Asciidoc itself.
Build Gadget Server
mvn clean install
Use the maven 3.0.3 version or above.
Deploying Gadget Server
Find gadget-server-1.0.0-SNAPSHOT.zip from the target directory under distribution module.
Unzip gadget-server-1.0.0-SNAPSHOT.zip, follow the readme from gadget-server-1.0.0-SNAPSHOT.zip to deploy the gadget server into AS7 (The AS7 version needs to be 7.1.1.Final or higher)