Fix mongoose promise deprecation (#285)
Fix mongoose promise deprecation (#285)

Mongoose updated and dropped support for its own promise library
mpromise. The test will now rely on builtin promises.

PR-URL: https://github.com/GoogleCloudPlatform/cloud-trace-nodejs/pull/285

The changelog claims that mongoose will use native promises but the
deprecation warning still happens. We will use their recommended work
around:
https://github.com/Automattic/mongoose/wiki/5.0-Deprecation-Warnings
keymetrics/trassingue,googleapis/cloud-trace-nodejs,googleapis/cloud-trace-nodejs,keymetrics/vxx,keymetrics/trassingue,matthewloring/cloud-trace-nodejs,matthewloring/cloud-trace-nodejs,googleapis/cloud-trace-nodejs,googleapis/cloud-trace-nodejs,matthewloring/cloud-trace-nodejs,keymetrics/vxx