Added User to Feeds ACLs - closes #6

- RSSAPI\Response object now properly checks user ACLs
- Added two new commands `rssapi user addsuper` and `rssapi user attach`
  - `rssapi user addsuper [email] <password>` - same as add, but added
    user is a super user (he can see all the groups and feeds)
  - `rssapi user attach` - displays list of users, then list of feeds.
    If both user and feed are chosen, selected feed will be attached to
    selected user (he will be able to fetch it)
- Fixed `rssapi feed fetch` (was totally broken due to existing feed
  exception)