Force all operations to happen FIFO on background NSOperationQueue
Timestamping, apiKey set immediately on main thread
All calls to uploadEvents to happen on background thread
Start/end session calls to happen on main thread to ensure proper ordering of added events
Delete old events every 20 beyond 1000 events
Added logPurchase: method
Location manager only update once on start
Don't listen for location updates, only grab the most recent location
Added max_id tracking to propertyList to attempt to resolve percentage of events not tracked
Removed duplicate properties field from events (now only api_properties exists)
changed logPurchase method to logRevenue and price argument to amount
Added fix for event deletion in middle of an upload so a successful upload removes the correct number of events