Does not generate urls

[bitboxer]

I just tried to use the plugin, but I could not get it working.

I added a _i18n.de.yml with this content:

de:
  title: "Hallo!"

In the index.md I added this line:

# {% t title }

And now the only thing that is generated is the /index.html with this content:

# translation missing: und.title

There is no file generated with the language as prefix.

I am using jekyll 2.5..1 right now.

What have I done wrong?