changelog: prepare for v0.0.7
-2018-xx-xx: v0.0.7
+2018-07-24: v0.0.7
1.5.x protobuf support
operations: new helpers for additional offer operations
scheduler/calls: new helpers for ack offer op update AND reconcile offer op
master: helpers for teardown and mark-agent-gone
additional test cases for new reservation validation
operations: support reservation refinements
+ lib: formatting options for resource stringification
+ httpsched: connectivity listener/notification API
+ ci: drop golang 1.7.x, add 1.9.x, 1.10.x
2018-03-12: v0.0.6
1.4.x protobuf support
