v3.6.0

This release makes the following changes:

• Tracing support for bluebird Promises has been added. Since Knex-specific tracing patches were being applied because it was using bluebird, the Knex patch has been removed. We don't expect Knex users to observe significant changes.
• Child spans can now extend longer than their parents.

Commits

6148c71 chore(deps): update dependency retry-axios to ^0.5.0 (#979)
ea9cb4b fix(deps): update dependency gcp-metadata to v1 (#975)
29bb15c feat: support context propagation in bluebird (#872)
990bfe0 chore(deps): update dependency mocha to v6 (#976)
3259d8d chore(deps): update dependency standard-version to v5 (#974)
82e4c24 test: don't make network request in gRPC context test (#970)
79e26a9 build: use linkinator for docs test (#972)
fccfd92 docs: update links in contrib guide (#973)
583b5a7 chore(deps): update dependency @types/tmp to v0.0.34 (#971)
ad1bdca test: stop requiring request (#969)
8be83d8 chore(deps): update dependency ts-node to v8 (#960)
6535193 test: test hapi tails (#968)
adc666e docs: note on using trace in bundled server code (#967)
5e3c896 build: create docs test npm scripts (#966)
7b84349 fix(deps): update dependency @google-cloud/common to ^0.31.0 (#963)
d1de959 feat: support child spans with tail latencies (#913)
f88cdd4 Automerge by dpebot
a821462 fix(deps): update dependency @google-cloud/datastore to v3 (#951)
95895a8 chore(deps): update dependency @grpc/proto-loader to ^0.4.0 (#957)