Google Reader starred.json importer

Hey there, wrote a somewhat hacked together piece of code to import starred items from a starred.json file. Worked for me on an initial bit of testing, though it'll ignore stars on feeds that aren't subscribed to.

How it works currently is that it'll go through items (that are part of currently subscribed feeds), adds them if they don't exist (code needs cleaning up), and then set them to read + starred.

Definitely not expecting to get it merged in its current state, but I'd like to get feedback on how it'd be best integrated into the app.

My thoughts are renaming `/starred` to `/stars`, which would then make sense for an import URL to be `/stars/import`. Though since this code is pretty specific to Google Reader unlike `/feeds/import`, maybe an import page dedicated to Google Reader is better?

On that note -- I've only written importing for starred.json instead of the entirety of a Google Takeout file, since I haven't made use of the other features such as following, notes, liking etc.

- [ ] Clean up code
- [ ] Add localised text
- [ ] Add tests
- [ ] Fix ignoring stars on non-subscribed feeds (how?)