Add TopicId and SubscriptionId classes#984

Merged

mziccard merged 4 commits intogoogleapis:pubsub-alphafrom

mziccard:pubsub-ids

May 10, 2016

Commits on May 5, 2016

Add TopicId class and tests. Use TopicId in SubscriptionInfo
mziccard
committed
Add SubscriptionId class and tests. Use SubscriptionId in listSubscriptions(topic)
mziccard
committed

Commits on May 6, 2016

Minor javadoc fixes
mziccard
committed

Commits on May 9, 2016

Add identity for deleted topics
mziccard
committed