doc(Auth-with-Ionic3-Angular4.md): Updated guide to use Ionic 3 and Angular 4

* Auth-with-Ionic3-Angular4.md

Facebook Authentication with Angular4-Ionic3 and AngularFire2

* Update Auth-with-Ionic3-Angular4.md
* Update README.md
* Updated Dev Guid to add entry for linking AngularFire2 with Ionic 3 and Angular4.
* Update Auth-with-ionic3-Angular4.md

Updated the document at the start, to explicitly call out, this tutorial uses Facebook as the sign-in provider.

* Update Auth-with-Inoci3-Angular4.md

Updated document to take advantage of tree shaking.

* Update Auth-with-Ionic3-Angular4.md

Corrected the facebook imports and removed photoURL property as it was giving 403 errors.
Need to look into the issue and will get it added later. App works fine on both browser and mobile.

* Update Auth-with-ionic3-Angular4.md

Removed an additional if block that checked "cordova" platform twice and returned promise.

* Update Auth-with-Ionic3-Angular4.md

Rephrased the sentence to  clarify installation of Angular4/AngularCLI

Author: mukesh51

README.md

@@ -61,3 +61,4 @@ productive with AngularFire2.
 4. [Querying lists](docs/4-querying-lists.md)
 5. [User Authentication - FirebaseAuthentication](docs/5-user-authentication.md)
 6. [Using AngularFire2 with Ionic 2](docs/Auth-with-Ionic2.md)
+7. [Using AngularFire2 with Ionic 3 and Angular 4](docs/Auth-with-Ionic3-Angular4.md)