The p2 update site for antlr4 sources.
Building a p2 update site for a maven plugin was realized using the 'p2-maven-plugin' maven plugin which can be found at https://github.com/reficio/p2-maven-plugin.
The idea of building the p2 update site using TravisCI and make it available on GitHub through GitHub Pages comes from the following post https://github.com/steveklabnik/automatically_update_github_pages_with_travis_example