Bring macros to IRC

Summary:
Adds a macro handler that spams your channel with macros. Config is:

• macro.size: scale macros to this size before rasterizing
• macro.sleep: sleep this many seconds between lines (evade flood protection)

Test Plan: derpderp

Reviewers: kdeggelman, btrahan

Reviewed By: btrahan

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1838