Use JDK 8 for release

[mdedetrich]

Not sure why the -release:8 scalac flag didn't work when releasing a new version but one way to enforce JDK 8 compatibility is to just use JDK8 when releasing.

Also since we are building against JDK 8, I added it to the normal CI to make sure we don't break JDK 8 compatiblity

[mdedetrich]

@ruippeixotog So if you look at the CI run in this PR against JDK 8 I think I figured out the issue, it appears that the problem is in a dependency , i.e. org/eclipse/jgit/storage/file/FileRepositoryBuilder. This has been solved in a separate PR made at #253.

This means that the -release:8 argument technically speaking is working because its making sure that this project emits JDK 8 compatible bytecode but of course it cannot magically convert the dependencies of this project to also target JDK 8.

[ruippeixotog]

Thanks for the quick fix, @mdedetrich! Agree that the best way to guarantee it works with JDK 8 (including dependencies) is to have CI use it.

[rolandtritsch]

Also since we are building against JDK 8, I added it to the normal CI to make sure we don't break JDK 8 compatiblity

Agreed. Merged. Thanks for the fix.