Fix Jest error.

Background: Running Jest without the testUrl option results in the following error:

"localStorage is not available for opaque origins"

jestjs/jest#6766

src/configs/jest/config.js

@@ -6,11 +6,12 @@ const here = (p) => path.join(__dirname, p);
 const useBuiltInBabelConfig = !hasFile('.babelrc') && !hasPkgProp('babel');
 
 const jestConfig = {
-  rootDir: fromRoot('src'),
   coverageDirectory: path.join(fromRoot('src'), '../coverage'),
+  rootDir: fromRoot('src'),
   setupFiles: [here('../enzyme/config.js')],
   setupTestFrameworkScriptFile: here('./setup.js'),
   snapshotSerializers: ['enzyme-to-json/serializer'],
+  testURL: 'http://localhost',
 };
 
 if (useBuiltInBabelConfig) {