Can't make i18n run
The documentation for this library is a mess, mostly because the author decided to rewrite it from version 1.x to 2.x and the API has changed drastically. The documentation you can now find on http://i18next.com/docs/ refers to version 2.x, while a lot of the blog and stackoverflow articles refer to version 1.x, adding to the confusion. To add insult to injury, I can't find any complete documentation for version 1.x anymore (which by the way, is less than a year old).
Now, to answer your question, the options and API you seem to be using are from version 1.x (for example, resGetPath doesn't exist in version 2.x). Also, in 2.x, i18n has been replaced by i18next.
On the bright side, the author seems to reply fast to questions, so you might as well open an issue on the project github page. Or check this: