Add batch function to core/utils.js
Aggregate watch changes by folder
watcher: only aggregate folders with many events

Still send out single events when aggregation is not useful
Fix: export batch function in utils
Fix minor errors with our batch processor in cb.watch
Fix: flipped condition in core/utils.js batch
Merge pull request #203 from FriendCode/fix/watcher_overload

Batch process watcher events to avoid overloading