Add support to run JavaFX tests on Travis

[chahuistle]

I don't have the time right now to keep working on this one, but this how I found this problem:

• All unit tests passed locally using IntelliJ and OpenJDK 8.
• Travis' java compiler (OpenJDK 8) complained about not finding JavaFX symbols.
• I spent a few minutes on Google, tried a couple of things but I could not get to compile JavaFX code using Ubuntu Trusty images in Travis (OpenJDK 8).
• I changed to Oracle's JDK 8 in Travis, now the code compiled, but the jUnit ToolExecutorJavaFXTest.testWithEmptyToolProperties errored.
• I enabled debug in Maven and still got no more information.
• After inspecting the erroring jUnit, I realized that I left that jUnit there by mistake.
• Since I spent so much time figuring this one out, I thought that maybe it was worthy of writing an issue.

After that, in my frustration, I decided to simply add the @Ignore annotation.

I suggest to work on this one after this issue has been closed.

[chahuistle]

Also, I found out that there is a way to enable JavaFX in headless mode using a library called monocle.

This is what I found out when I realized that maybe this is something that I should document: https://nofluffjuststuff.com/blog/andres_almiray/2016/02/running_testfx_tests_in_headless_mode

[chahuistle]

Moved to https://github.com/qbicsoftware/javafx-utils-lib/issues/1