flyspell-languagetool does not seem to work out of the box

[ACoquereau]

The grammar checker languagetool does not seem to work from a fresh install (with commit a09b742).

I try to m-x flycheck-languagetool-flycheck-enable on an OCaml file, and it did nothing (no log in *messages*). On a .rst file I got flycheck-add-next-checker: nil is not a valid syntax checker