Fix errors from backbone.paginator when filtering results

Summary:
Filtering results after paging sometimes ends up with us being on an
out of bounds page. Instead we always reset to the first page when
filtering the results.

Fixes T330

Test Plan:
As per T330
- go to home page, get 156 results by default
- click page 2 or later
- select a tag, search
- list does not change, error in console

Reviewers: dkobia, shadowhand

Reviewed By: shadowhand

Maniphest Tasks: T330

Differential Revision: https://phabricator.ushahidi.com/D161