Requiring js files from data dir fails if jshint is used as dep

Commit 7f694e45d makes use of js files inside the data dir.
However, if you npm install jshint as a dependency on one of
your projects, you will notice the data dir is not present.
This is because the data dir is deleted as part of the installation
procedure. I am not sure whether such files should be moved to the
src dir (which is kept) or if data should not be removed
in the first place. I have no opinion on that but I decided to
make a pull-request that fixes the latter.