Oh damn... Sorry Trixt0r but I completely forgot to mention that I tried your importer too !
But in fact, I didn't success to make it works. At the moment, I just retry to use it and it was a success ! Your library seems to work perfectly.
My problem was that I tried to use the code in folder "spriter-test" instead of "Spriter" and "Spriter-desktop". (Due to the commentaries in your GitHub repository, speaking about LibGDX tests in this folder)
To conclude : Great thanks for your Spriter Importer, it works like a charm, I hope that you will maintain it in the future.