Chatlog - add a pager
Summary: 'cuz I miss out on chat room goodness and can't paginate around in the current version
Test Plan: setup a phabot and spammed it in phabot-test. with new test data, set $page_limit = 1 and paged about -- looks good!
Reviewers: epriestley
Reviewed By: epriestley
CC: aran, epriestley
Maniphest Tasks: T990
Differential Revision: https://secure.phabricator.com/D2032