Switch to the iHackerNews API (Fix #2) + Add text filter

- Due to non-resolved encoding errors in the HN Droid API
  (https://github.com/glebpopov/Hacker-News-Droid-API/issues/4), decided
to switch to the iHackerNews API (no API key required)
- Added the ability to filter the list of items using Alfred query, (ie
  "hn google")