Add initial set of material tests (#761)

* Add initial set of material tests
* Add test package with common helpers

Author: eneufeld

.gitignore

@@ -2,6 +2,7 @@ node_modules
 coverage
 .nyc_output
 dist
+lib
 *.log
 
 .idea/

packages/core/test/dispatch.renderer.test.tsx

@@ -18,7 +18,7 @@ import {
   findRenderedDOMElementWithTag,
   renderIntoDocument,
   scryRenderedDOMElementsWithTag
-} from '../../vanilla/test/helpers/react-test';
+} from '../../test/helpers/react-test';
 
 class CustomRenderer1 extends Renderer<RendererProps, any> {
   render() {