This prevents the .test-container selector to appear twice in our test
markup:
```html
<div class="test-container passed" id="camunda-properties simple should
open stuff">
<div class="title-row">
<a href="#camunda-properties%20simple%20should%20open%20stuff">
<h3 class="test-titel">camunda-properties simple should open
stuff</h3>
</a>
<div class="test-result" style="float: right;">passed</div>
</div>
<div class="test-content-container test-container">
<!-- test content -->
</div>
</div>
```
With this commit we only add the .test-content-container marker in cases
where `mocha-test-container-support` is not present upon running
`bootstrapBpmnJS`.
This commit promisifies following APIs:
BaseViewer#importXML
BaseViewer#importDefinitions
BaseViewer#open
BaseViewer#saveXML
BaseViewer#saveSVG
Modeler#createDiagram
Related to https://github.com/bpmn-io/bpmn-js/issues/812
BREAKING CHANGES:
* Users are now expected to have Promises either by default or
polyfilled as the APIs return a Promise now.
* use ES6 import / export
* UTILS: export individual utilities
* TESTS: localize TestHelper includes
BREAKING CHANGE:
* all utilities export independent functions
* library sources got ported to ES6. You must now use
a ES module bundler such as Browserify + babelify or
Webpack to consume this library (or parts of it).
This commit extracts the test helper utility to its own module.
Use in bpmn-js extensions via
var Helper = require('bpmn-js/test/helper');
This adds the global helper bindings bootstrapModeler/Viewer and inject.