behat-ss is not ready for Travis

[robbieaverill]

I just had a quick go at swapping Travis config over to use vendor/bin/behat-ss instead of vendor/bin/behat (commit: creative-commoners/silverstripe-versioned-admin@b6611f9).

The tests pass, but stdout is full of network requests: https://travis-ci.org/creative-commoners/silverstripe-versioned-admin/jobs/421364280

Example:

@javascript
Feature: View a version
  As a cms author
  I want to view a version
  Background:                                                    # tests/Behat/features/view-a-version.feature:6
    Given a "page" "Home" with "Content"="Welcome to my website" # SilverStripe\VersionedAdmin\Tests\Behat\Context\FixtureContext::stepCreateRecordWithData()
    And I have a config file "enable-historyviewer.yml"          # SilverStripe\Framework\Tests\Behaviour\ConfigContext::stepIHaveConfigFile()
    Given I am logged in with "ADMIN" permissions                # SilverStripe\BehatExtension\Context\LoginContext::iAmLoggedInWithPermissions()
[Tue Aug 28 01:38:02 2018] 127.0.0.1:58360 [200]: /resources/silverstripe/admin/client/dist/styles/bundle.css?m=1535420065
[Tue Aug 28 01:38:02 2018] 127.0.0.1:58458 [200]: /resources/silverstripe/asset-admin/client/dist/styles/bundle.css?m=1535420078
[Tue Aug 28 01:38:02 2018] 127.0.0.1:58362 [200]: /resources/silverstripe/cms/client/dist/styles/bundle.css?m=1535420075
[Tue Aug 28 01:38:02 2018] 127.0.0.1:58460 [200]: /resources/silverstripe/campaign-admin/client/dist/styles/bundle.css?m=1535420072
[Tue Aug 28 01:38:02 2018] 127.0.0.1:58462 [200]: /client/dist/styles/bundle.css?m=1535419980
[Tue Aug 28 01:38:02 2018] 127.0.0.1:58468 [200]: /resources/silverstripe/admin/client/dist/styles/browser-warning.css?m=1535420065
[Tue Aug 28 01:38:02 2018] 127.0.0.1:58470 [200]: /resources/silverstripe/admin/client/dist/js/vendor.js?m=1535420065
[Tue Aug 28 01:38:02 2018] 127.0.0.1:58472 [200]: /resources/silverstripe/admin/client/dist/js/bundle.js?m=1535420064
[Tue Aug 28 01:38:02 2018] 127.0.0.1:58474 [200]: /resources/silverstripe/admin/thirdparty/bootstrap/js/dist/util.js?m=1535420065
[Tue Aug 28 01:38:02 2018] 127.0.0.1:58476 [200]: /resources/silverstripe/admin/thirdparty/bootstrap/js/dist/collapse.js?m=1535420065
[Tue Aug 28 01:38:03 2018] 127.0.0.1:58478 [200]: /resources/silverstripe/admin/client/lang/en.js?m=1535420065

It looks like this is because the piping is different (from behat to behat-ss):

- chromedriver > artifacts/chromedriver.log 2>&1 &
+ chromedriver &> artifacts/chromedriver.log 2> artifacts/chromedriver-error.log &

I think it'd be a good idea to start using behat-ss in Travis, but perhaps in order to do this we'd need to pipe stderr into stdout and log it all together.

How do you feel about this @tractorcow?