implement multiple users; pre-create them in the view.
setting pct videos by querystring arg
make the number of users configurable as well, defaulting to old value (1)
implementing logouts
fixing js bug
use backbone isFunction method
Merge pull request #609 from bcipolli/multiuser_loadtest

Multiuser loadtest
Thanks @jamalex !  This tool was super-useful for me to test UserLog functions!