Updates to multiplexer_test.dart
Rename multiplexer_test to handler_test.
Merge with latest changes.
Merge pull request #205 from alxhub/master-v0.2

Refactor and rename multiplexer_test to handler_test and include in all_tests.dart.
isPrimary now takes an AssetId instead of an Asset.
Merge pull request #206 from alxhub/fix-barback

Barback version update changed isPrimary() - now takes an AssetId instead of an Asset
Consolidate & fix raw and wrapper tests
Split marshalling tests from entity tests
Move base tests to separate file