electron update

Summary:
Started with upgrading electron from 3.0.0 to 4.0.5. This required a bunch of subsequent updates:
* upgrading `electron-builder` to latest version, because the old version couldn't build electron 4 apps.
  * `appDir` is deprecated in builder config, `projectDir` is used instead, which we already had set, so its fine to just remove this ([see GitHub commit](a5e457163e)).
* upgrading `jest-runner/electron` because the old version couldn't run electron 4 tests.
  * upgrading our custom dependency resolution to use electron 4.0.5, because the test runner still resolves to 2.0.8 ([see GitHub issue](https://github.com/facebook-atom/jest-electron-runner/issues/31)).
* updating `sandcastle.sh` to use the new cache files from D14131344.
* removing `package-lock.json` as is was causing warnings. We use `yarn` and `yarn.lock` anyways. This file must have been committed by accident.
* updating our check to only run one version of Flipper at a time to use the new electron API `app.requestSingleInstanceLock` as the old one was removed in electron 4.
* updating the snapshot test that checks App rendering, which changed a little due to the electron upgrade.
* upgrading flow-type definitions to `electron-v4.0.5.js` generated by [electron-flowtype-definitions](https://github.com/danielbuechele/electron-flowtype-definitions).

**PS: Best new feature in Electron 4: Copy&paste working in dev tools**

Reviewed By: jknoxville

Differential Revision: D14131360

fbshipit-source-id: d7ed9643875629a1fa1860bb61b11dd0c64112ab

static/index.js

@@ -100,22 +100,23 @@ compilePlugins(
 });
 
 // check if we already have an instance of this app open
-const isSecondInstance = app.makeSingleInstance(
-  (commandLine, workingDirectory) => {
-    // someone tried to run a second instance, we should focus our window
+const gotTheLock = app.requestSingleInstanceLock();
+
+if (!gotTheLock) {
+  app.quit();
+} else {
+  app.on('second-instance', (event, commandLine, workingDirectory) => {
+    // Someone tried to run a second instance, we should focus our window.
     if (win) {
       if (win.isMinimized()) {
         win.restore();
       }
-
       win.focus();
     }
-  },
-);
+  });
 
-// if this is a second instance then quit the app to prevent collisions
-if (isSecondInstance) {
-  app.quit();
+  // Create myWindow, load the rest of the app, etc...
+  app.on('ready', () => {});
 }
 
 // quit app once all windows are closed