Drop (official) support for running on java 7
Drop (official) support for running on java 7

We still compile with "targetCompatibility = 1.7", but don't run
integration tests on Java 7 JVMs.

This also takes care of https://github.com/gradle/gradle/issues/2421

sherter/google-java-format-gradle-plugin,sherter/google-java-format-gradle-plugin