docs: Correcting errors in methods and types

Author: markgoho

docs/Auth-with-Ionic2.md

@@ -268,26 +268,22 @@ import * as firebase from 'firebase/app';
 
 @Injectable()
 export class AuthService {
-  private authState: Observable<firebase.User>;
   private currentUser: firebase.User;
 
   constructor(public afAuth: AngularFireAuth) {
-    this.authState = afAuth.authState;
-    afAuth.subscribe((user: firebase.User) => {
-      this.currentUser = user;
-    });
+    afAuth.authState.subscribe((user: firebase.User) => this.currentUser = user);
   }
 
   get authenticated(): boolean {
     return this.currentUser !== null;
   }
 
-  signInWithFacebook(): firebase.Promise<FirebaseAuthState> {
+  signInWithFacebook(): firebase.Promise<any> {
     return this.afAuth.auth.signInWithPopup(new firebase.auth.FacebookAuthProvider());
   }
 
   signOut(): void {
-    this.afAuth.signOut();
+    this.afAuth.auth.signOut();
   }
 
   displayName(): string {
@@ -478,21 +474,17 @@ import { Facebook } from 'ionic-native';
 
 @Injectable()
 export class AuthService {
-  private authState: Observable<firebase.User>;
   private currentUser: firebase.User;
 
   constructor(public afAuth: AngularFireAuth) {
-    this.authState = afAuth.authState;
-    afAuth.subscribe((user: firebase.User) => {
-      this.currentUser = user;
-    });
+    afAuth.authState.subscribe((user: firebase.User) => this.currentUser = user);
   }
 
   get authenticated(): boolean {
     return this.currentUser !== null;
   }
 
-  signInWithFacebook(): firebase.Promise<FirebaseAuthState> {
+  signInWithFacebook(): firebase.Promise<any> {
     if (this.platform.is('cordova')) {
       return Facebook.login(['email', 'public_profile']).then(res => {
         const facebookCredential = firebase.auth.FacebookAuthProvider.credential(res.authResponse.accessToken);
@@ -505,7 +497,7 @@ export class AuthService {
   }
 
   signOut(): void {
-    this.afAuth.signOut();
+    this.afAuth.auth.signOut();
   }
 
   displayName(): string {