Make compatible with modules

[bowbahdoe]

This PR

• Adds a module-info.java so that this can be used in modular projects that want to use jlink via the Multi Release Jar mechanism
• Moves tests on travis CI to use java 9 because I couldn't think of another way.

My motivation here is kinda simply to parse a toml file in my modular app.

[thelooter]

I've forked this repo into https://github.com/thelooter/toml4j. Are you fine with me cherry-picking your changes into my tree?

[bowbahdoe]

@thelooter go for it.

Are you planning on doing any other "modernization" type things on your fork? Let me know how i can be of use

[thelooter]

I'm currently trying to get a grip on how everything works, restructure stuff so it's not just everything in one package and then see where this leads me