WIP tests(login): signin and signup tests for about:accounts


Fixes https://github.com/mozilla/fxa-content-server/issues/1558
Out of personal curiosity, is this any different than just doing something like:
```js
var fxaAuthRoot = args.fxaAuthRoot || 'http://127.0.0.1:9000/v1';
var fxaContentRoot = args.fxaContentRoot || 'http://127.0.0.1:3030/';
var fxaEmailRoot = args.fxaEmailRoot || 'http://127.0.0.1:9001';
var fxaOauthApp = args.fxaOauthApp || 'http://127.0.0.1:8080/';
var fxaProduction = args.fxaProduction || false; // or possibly even `!!args.fxaProduction;`
var fxaToken = args.fxaToken || 'http://';
```