Rolled back some changes that were breaking behavior.

Included other input keyboards (Spanish keyboard @ was not triggering the search).

Some improvements:
- If contacts added or edited, the cache is refreshed.
- Trimmed spaces at the beginning of the search text
- Backspace on empty search removes the search box
- Disabled button if there are not contacts to search for (i.e. address book empty)
- some minor UI improvements to the search results

The README has been changed. Screenshots included.