Update result list on user typing, not just when filter is empty

[toppsdown]

Currently At.JS only supports refreshing results from the server when the filtered list is empty See RemoteFilter

This can lead to a problem when there are matches not included in the original set of returned results

Use case:

1. AtWho initializes with first 10 users from server. One of these users is named "Bob 1"
2. Use begins typing "Bob" and atwho filters the list to show "Bob 1"
3. User actually wants to tag "Bob 2" who was not included in the first set of results. At.JS never queries the server again