Add Voyageur.monitor_connection, although it needs to be excluded from the ajaxStart/ajaxError functions
ping failures enter offline mode, disabling sync; persist collection when ping is restored
Add Home#ping to reduce server load for keepalive pings
Move spinner to Backbone.sync and show a warning when syncing fails
Re-implement TripsController#update to handle updating after downtime
Fix data-trip-position attrs on specs now that indices are calculated from 0 in the javascript.
Merge branch 'server_monitor' into development