Rough perf tests
#on() perf increase for adding one, multiple, or an array of callbacks
#off() perf increase for removing one, multiple, or an array of callbacks
#fire() perf increase when triggering event with arguments
Removed _each() helper as it's no longer used
Removed copy of slice(). No longer needed - was hampering performance
Fiddled with Array.isArray polyfill
Added require.js support. Version bump. Includes performance enhancement mostly from no longer using array slice