Add support for Java 9!

Please add support for Java 9 too.

The Travis-CI relevant part of the build matrix for Java 9:

    - dist: trusty
      group: edge
      jdk: oraclejdk9
      sudo: required
      addons:
        apt:
          packages:
            - oracle-java9-installer

Thank you.

Yes, but have to wait until all dependencies support Java 9.

I know that RichTextFX does not yet support Java 9 (see https://github.com/TomasMikula/RichTextFX/issues/270). And maybe also Flowless.

Fixed in 1.0: https://github.com/JFormDesigner/markdown-writer-fx/releases