minor grammar fix

docs/version-4-upgrade.md

@@ -1 +1,117 @@
+AngularFire2 4.0 is a refactor of the AngularFire2 package which implements
+@NgModule, simplifies authentication, and better supports Angular 4.
 
+### Removing `AngularFire` for Modularity
+
+Prior to 4.0, AngularFire2 did not take advantage of the Firebase SDK's modularity for tree shaking. The `AngularFire` service has now been removed and the library is broken up into smaller `@NgModule`s:
+
+* `AngularFireModule`
+* `AngularFireDatabaseModule`
+* `AngularFireAuthModule`
+
+When upgrading, replace calls to `AngularFire.database` and `AngularFire.auth` with `AngularFireDatabase` and `AngularFireAuth` respectively.
+
+```typescript
+constructor(af: AngularFire) {
+  af.database.list('foo');
+  af.auth;
+}
+```
+Should now be:
+
+```typescript
+constructor(db: AngularFireDatabase, afAuth: AngularFireAuth) {
+  db.list('foo');
+  afAuth.authState;
+}
+```
+
+### Simplified Authentication API
+
+In 4.0 we've reduced the complexity of the auth module by providing only [`firebase.User`](https://firebase.google.com/docs/reference/js/firebase.User) observers (`AngularFireAuth.authState`, `AngularFireAuth.idToken`) and cutting the methods that were wrapping the Firebase SDK.
+
+
+```typescript
+import { AngularFireAuth } from 'angularfire2/auth';
+// Do not import from 'firebase' as you'd lose the tree shaking benefits
+import firebase from 'firebase/app';
+...
+
+user: Observable<firebase.User>;
+constructor(afAuth: AngularFireAuth) {
+  this.user = afAuth.authState; // only triggered on sign-in/out (for old behavior use .idToken)
+}
+```
+
+AngularFire2 exposes the raw Firebase Auth object via `AngularFireAuth.auth`. For actions like login, logout, user creation, etc. you should use the [methods available to `firebase.auth.Auth`](https://firebase.google.com/docs/reference/js/firebase.auth.Auth).
+
+While convenient, the pre-configured login feature added unneeded complexity. `AngularFireModule.initializeApp` no longer takes a default sign in method. Sign in should be done with the Firebase SDK via `firebase.auth.Auth`:
+
+```typescript
+login() {
+  this.afAuth.auth.signInWithPopup(new firebase.auth.GoogleAuthProvider());
+}
+logout() {
+  this.afAuth.auth.signOut();
+}
+```
+
+### FirebaseListFactory and FirebaseObjectFactory API Changes
+
+If you directly use `FirebaseListFactory` or `FirebaseObjectFactory` you will no longer be able to pass in a string, it will instead expect a Firebase database reference.
+
+## Putting this all together
+
+Here's an example of what AngularFire2 4.0 looks like:
+
+```typescript
+import { NgModule, Component } from '@angular/core';
+import { Observable } from 'rxjs/Observable';
+import { AngularFireModule } from 'angularfire2';
+import { AngularFireDatabaseModule, AngularFireDatabase, FirebaseListObservable } from 'angularfire2/database';
+import { AngularFireAuthModule, AngularFireAuth } from 'angularfire2/auth';
+import { environment } from '../environments/environment';
+
+// Do not import from 'firebase' as you'd lose the tree shaking benefits
+import firebase from 'firebase/app';
+
+
+@NgModule({
+  declarations: [ App ],
+  exports: [ App ],
+  imports: [ 
+    AngularFireModule.initializeApp(environment.firebase, 'my-app'),
+    AngularFireDatabaseModule,
+    AngularFireAuthModule
+  ],
+  bootstrap: [ App ]
+})
+export class MyModule { }
+
+```
+
+```typescript
+@Component({
+  selector: 'my-app',
+  template: `
+    <div> {{ (items | async)? | json }} </div>
+    <div> {{ (user | async)? | json }} </div>
+    <button (click)="login()">Login</button>
+    <button (click)="logout()">Logout</button>
+  `
+})
+export class App {
+  user: Observable<firebase.User>;
+  items: FirebaseListObservable<any[]>;
+  constructor(afAuth: AngularFireAuth, db: AngularFireDatabase) {
+    this.user = afAuth.authState;
+    this.items = db.list('items');
+  }
+  login() {
+    this.afAuth.auth.signInWithPopup(new firebase.auth.GoogleAuthProvider());
+  }
+  logout() {
+     this.afAuth.auth.signOut();
+  }
+}
+```