Feature/langloc

This will return a client.json file based on user preference.
It will work from most preferred to least, to "en" as the default.
It also presumes all pathnames are in lower case (because LCD)

@kitcambridge, @nchapman r?
Is this valid syntax? [RFC 7231](http://tools.ietf.org/html/rfc7231#section-5.3.5) provides `da, en-gb;q=0.8, en;q=0.7` as an example; Firefox sends `en-US,en;q=0.5`. Not sure if it's legal to omit the "q" character.