Add Promise.try polyfill

[dpogue]

There are a bunch of places that we're using a pattern like return Promise.resolve().then(...) which has a very slight async penalty and can make stacktraces a bit harder to read.

We should replace these with a Promise.try polyfill, like proposal-promise-try or p-try.

[xeoneux]

I'd like to give it a try

[raphinesse]

Once we drop support for Node.js 6 it's probably better to use async functions instead of any Promise.try implementation.

[raphinesse]

Closing in favor of apache/cordova#175