Implement polling request manager

Request manager pulls requests off queue at a rate based on server responses
Merge branch 'master' into polling-request-manager
Add logging and ensure requestManager API doesn't depart from original too much
Don't reset timer when we get a successful response
Use exponential back-off to find acceptable polling rate
Fix typos and silly mistakes
Merge branch 'master' into polling-request-manager

Conflicts:
	lib/requestManager.js
Use request manager as singleton