Lanterna 3.1 update

[Martin]

Hi everyone,

I've spent some time over the new year holidays to bring Lanterna 3.1 into shape, which includes:

 * Java 8 source level (with code migrated to Java 8 syntax)

 * Java 9 module support

 * Improved Menu system

 * New Table implementation

 * Some minor features that weren't backported to 3.0

I'm intending to do an alpha release to Sonatype soon:ish and update the Github documentation. Also, I think another 3.0 bugfix release is overdue. After this, I don't really have any further plans for the library other than bugfixes.

Regards,

Martin