Gson Version 2.2.2 is very old (July 2012) which makes impossible to integrate libs which require a more recent version of gson.

[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] — maven-dependency-plugin:2.8:tree (default-cli) @ riedel —
[INFO] at.pixelart.riedel:riedel:pom:1.0-SNAPSHOT
[INFO] - info.magnolia.pages:magnolia-pages-app:jar:5.5.6:compile
[INFO] - info.magnolia.ui:magnolia-ui-vaadin-integration:jar:5.5.6:compile
[INFO] - com.google.code.gson:gson:jar:2.2.2:compile
[INFO]