Update enzyme usage for 3.1.0

Add a setup file that configures the React adapter. Fix one deprecated usage for ProjectLoaderHOC tests.

There are some tests still broken, but these weren't called out by Enzyme.

package.json

@@ -44,6 +44,7 @@
     "copy-webpack-plugin": "^4.0.1",
     "css-loader": "^0.28.7",
     "enzyme": "^3.1.0",
+    "enzyme-adapter-react-15": "1.0.1",
     "eslint": "^4.7.1",
     "eslint-config-scratch": "^5.0.0",
     "eslint-plugin-import": "^2.7.0",
@@ -98,6 +99,9 @@
     "xhr": "2.4.0"
   },
   "jest": {
+    "setupFiles": [
+        "<rootDir>/test/helpers/enzyme-setup.js"
+    ],
     "testPathIgnorePatterns": [
       "src/test.js"
     ],

test/helpers/enzyme-setup.js

+import Enzyme from 'enzyme';
+import Adapter from 'enzyme-adapter-react-15';
+
+Enzyme.configure({adapter: new Adapter()});

test/unit/util/project-loader-hoc.test.jsx

@@ -45,7 +45,7 @@ describe('ProjectLoaderHOC', () => {
         const before = mounted.find('div').text();
         ProjectLoader.load = jest.fn((id, cb) => cb(null, id));
         window.location.hash = `#winning`;
-        mounted.node.updateProject();
+        mounted.instance().updateProject();
         expect(mounted.find('div').text()).not.toEqual(before);
     });
 });