Add load simulator script

Fire up the load simulator by running ``bin/load-simulator.js``. Point
your browser to the URL for the first event (probably
``http://localhost:7777/event/1``), and you'll see lots of chat,
blurring, focusing, joining and leaving of the event.  Open up the
sessions, and people will join and leave those too.

Note: overrides SSL setting to not use SSL, so the mock users' sockets
can all connect properly without certificate validation issues.