Added server-side versioning and clientInterestChannel checks to deal with duplicates.
Removed lease times from data model as it will be handled by the channel.
Merge pull request #212 from qiangdavidliu/2.x

Duplicate interest handling
Merge remote-tracking branch 'remotes/netflix/2.x' into tbak/2.x

Conflicts:
	eureka-core/src/main/avro/eureka-registry-model.avdl