changelog: bump notes for 1.7.x protos, etc.
+2019-xx-xx: v0.0.9
+ 1.7.x protobuf support
+ resources: initial support for reservation-refinement in resource algebra, may be enabled
+ programmatically or at link-time via:
+ `-ldflags "-X github.com/mesos/mesos-go/api/v1/lib.CapabilityReservationRefinement=1"`.
+ controller: eventLoop returns context error if done
+ controller: WithContextPerSubscription
+ controller: option WithInitiallySuppressedRoles
+ backoff: avoid Timer.Reset() problems; honor minWait promise
+ httpsched: EndpointCandidates()
+
2018-07-26: v0.0.8
1.6.x protobuf support
