Move testUtil.js into src/app (#248)

testUtil contains some useful configuration endpoints for our frontend
testing. This commit moves it out of the artifact editor and up to
`src/app`.

Test plan: `yarn travis` passes.

src/plugins/artifact/editor/App.test.js

@@ -3,7 +3,7 @@ import React from "react";
 import ReactDOM from "react-dom";
 import App from "./App";
 
-require("./testUtil").configureAphrodite();
+require("../../../app/testUtil").configureAphrodite();
 
 // Check that PropTypes check out.
 it("renders without crashing", () => {

src/plugins/artifact/editor/ArtifactGraphEditor.test.js

@@ -7,8 +7,8 @@ import {Graph} from "../../../core/graph";
 import {ArtifactGraphEditor} from "./ArtifactGraphEditor";
 import {artifactAddress} from "../artifactPlugin";
 
-require("./testUtil").configureAphrodite();
-require("./testUtil").configureEnzyme();
+require("../../../app/testUtil").configureAphrodite();
+require("../../../app/testUtil").configureEnzyme();
 
 describe("ArtifactGraphEditor", () => {
   function createComponent(onChange) {

src/plugins/artifact/editor/ContributionList.test.js

@@ -12,8 +12,8 @@ import {AdapterSet} from "./adapterSet";
 import {ContributionList} from "./ContributionList";
 import {Graph} from "../../../core/graph";
 
-require("./testUtil").configureAphrodite();
-require("./testUtil").configureEnzyme();
+require("../../../app/testUtil").configureAphrodite();
+require("../../../app/testUtil").configureEnzyme();
 
 function createTestData(): * {
   type PayloadA = number;

src/plugins/artifact/editor/adapters/githubPluginAdapter.test.js

@@ -9,7 +9,7 @@ import {parse} from "../../../github/parser";
 import exampleRepoData from "../../../github/demoData/example-github.json";
 import adapter from "./githubPluginAdapter";
 
-require("../testUtil").configureEnzyme();
+require("../../../../app/testUtil").configureEnzyme();
 
 describe("githubPluginAdapter", () => {
   it("operates on the example repo", () => {