Implement batched tracking reqs + send when user idle
Implement batched tracking reqs + send when user idle

- now instead of sending a single XHR for each analytics event/link/page, it pools them up and sends all off in a single req when the user is idle or screen gets locked

Ensure req pool is only cleared if req successful

- if a req fails and we clear the pool, we've lost all those events
- instead just let it fail and we'll try again next time with the same events + whatever else happens

WorldBrain/WebMemex,WorldBrain/WebMemex