RESTful API

- `GET /feeds/`: Returns a list of feeds.
- `POST /feeds/`: Adds a new feed in OPML and crawl XML. Returns whether addition succeeded.
    - `url`: blog or feed url.
- `GET /feeds/<feed_id>/`: Returns entries of the feed.
    - `feed_id`: SHA1 encode of the feed url.
- `DELETE /feeds/<feed_id>/`: Removes the feed in OPML and feed XML. Returns whether deletion succeeded.
- `GET /feeds/<feed_id>/<entry_id>/`: Returns the entry content.