Renders the last 100 conpherence transactions only

Summary: Fixed T2428 a little bit

Test Plan: On trial, only the last n transactions loaded as hardcoded in ConpherenceViewController.php. Button was rendered.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2428

Differential Revision: https://secure.phabricator.com/D4898