Bump finagle and util version to 6.3.0
Add a RetriableReadableStore
Adding some comments
Add RetrableStore
Addressing the comments from @sritchie
Addressing Oscar's comments
Adding RetryingReadableStoreProperties
Use smaller timeout to expedite tests
Still use 6.2.1 for finagle-mysql
Merge pull request #89 from ximyu/develop

Add a retry combinator to Store