profiling
Merge branch 'master' into profiling

Conflicts:
	lib/src/publisher.dart
fielter fields support
Tomas's comments.
Profiling added.
bugfix, tests
Merge branch 'filter_fields_support' of github.com:cleandart/clean_sync into filter_fields_support

Conflicts:
	lib/src/mongo_provider.dart
Logger for profiling created.
Logging levels adjusted.
Merge pull request #39 from cleandart/filter_fields_support

Filter fields support