Merge pull request #156 from qiangdavidliu/2.x

Initial example interface/implementation of model and registry
Update registration/discovery protocol classes + verify transport compatibility.
Fix avro message broker failing tests.
Refactor transport implementation to be more flexible
with different protocol/codec implementations.
Add JSON codec for testing purposes.
Registration/discovery transport implementation - work in progress.
Merge pull request #159 from tbak/2.x

Eureka transport update.