This release adds support for Ruby 2.4.

• Update Datastore dependency to 0.24.x
• Update Error Reporting dependency to 0.23.x
• Update Natural Language dependency to 0.24.x
• Update Logging dependency to 0.24.x
• Update Monitoring dependency to 0.23.x
• Update Pub/Sub dependency to 0.23.x
• Update Speech dependency to 0.22.x
• Update Trace dependency to 0.23.x
• Update Vision dependency to 0.22.x