Update to dropbox.js 0.10.3

WIP. This fixes the OAuth flow on the desktop.

Dropbox complains with `Invalid client_id: "CBB0GYTWGYA=|aeSB7VBcIP94mzfQPoykIzGm++Z97KtaDn2snjXCGQ==".`, though. I'm guessing wherever you got your current one you could get a new (OAuth2) one?

However, are you actually supposed to put your key in the source here?