chore: release 2.0.0

[yoshi-automation]

🤖 I have created a release *beep* *boop*

2.0.0 (2019-05-17)

Bug Fixes

• deps: update dependency google-gax to ^0.26.0 (#606) (a637a68)
• Fix client pooling for long-lived listens (#614) (479bc9c), closes firebase/firebase-admin-node#499 #256
• deps: update dependency google-gax to v1 (#615) (687a353)
• run the generator (#616) (92b0add)
• docs: revert jsdoc and pin to 3.5.5 (#627) (e22f9c6)
• Support more than 100 long-lived streams (#623) (9474e3f)

Build System

• upgrade engines field to >=8.10.0 (#608) (32485f4)
• upgrade engines field to >=8.13.0 (#636) (a5db7d8)

Code Refactoring

• deprecation: remove deprecated getCollections() (#624) (43ac9c6)
• deprecation: remove legacy support for array arguments (#625) (54dd405)

BREAKING CHANGES

• library now requires Node >= 8.13.0
• deprecation: remove legacy support for array arguments (refactor(deprecation)!: remove legacy support for array arguments #625)
• deprecation: remove deprecated getCollections() (refactor(deprecation)!: remove deprecated getCollections() #624)
• upgrade engines field to >=8.10.0 (build!: upgrade engines field to >=8.10.0 #608)