feat(client): Forward the `resume` token to the auth server

feat(client): Seemless verification in a second browser.

* Create a `resume` token from OAuth parameters. Pass it along to the fxa-js-client.
* Re-populate OAuth parameters from resume token on email verification.
* Bump fxa-js-client to 0.1.25 with the new `resume` hotness.

Remaining work:
* [ ] - Merge #1665.
* [x] - Add some functional tests
* [x] - Check for missing parameters from the resume token. Allow user to finish verification, just do not allow redirect.
* [ ] - Check to make sure the serviceName is not displayed if the user is verifying in a second browser but they cannot redirect. When can this happen?

issue #1623
Nothing? Should the caller just check the response and ignore `resume` if it's null/undefined?