docs(): Update Auth-with-Ionic3-Augular4.md (angular#1171)

Fix promise-polyfill instruction and make tutorial less verbose

Author: gianpaj

docs/Auth-with-Ionic3-Angular4.md

@@ -1,48 +1,47 @@
 # Using AngularFire with Ionic
 
-This tutorial provides a walkthrough of integrating ANgularFIre Authentication with Ionic 3 /Angular 4+. 
-The below setup has been tested on Windows 10, but it should be same for Mac/Linux.
+This tutorial provides a walkthrough of integrating AngularFire Authentication with Ionic 3 /Angular 4+. 
+The below setup has been tested on Windows 10 and macOS Sierra, but it should be same for Linux.
 
 Note: - If you're working with Ionic2 and Angular2.0, then you should refer to **Auth-with-Ionic2** tutorial 
 [here](https://github.com/angular/angularfire2/blob/master/docs/Auth-with-Ionic2.md)
 
-Ensure that you're executing these commands as **Administrator** on Windows and **sudo** on Mac/Linux to avoid any errors.
+Ensure that you're executing these commands as **Administrator** on Windows and **sudo** on Mac/Linux if you get any permission errors.
 
-This tutorial uses **Facebook** as the sign-in provider. After completion of this tutorial, you should be able to configure
+This tutorial uses **Facebook** as the sign-in provider. After completing this tutorial, you should be able to configure
 other sign-in providers like **Twitter**, **Google** on your own.
 
 ### Prerequisites
 The first step is to ensure you have latest version of **Node** installed.
-You can get the latest version from [here](https://nodejs.org).
-This will install both node and npm.
+You can get the latest version from [nodejs.org](https://nodejs.org).
+This will install both `node` and `npm`.
 
 After installing node, check the version by executing the following command in your prompt window:
 
 ```bash
 
-C:\projects>node -v
+$ node -v
 v6.10.2
-
 ```
+
 As of this writing, this is the most stable version. If you're not on this version,
-please upgrade yourself to latest version by installing node from [here](https://nodejs.org).
+please upgrade yourself to latest stable version by installing node from [nodejs.org](https://nodejs.org).
 
 Check your npm version by executing the following command:
 ```bash
 
-C:\projects>npm -v
+$ npm -v
 3.10.10
-
 ```
 Install the Angular CLI, which will be used to build our Angular project and install Angular version 4 or later.
 
 ```bash
-C:\projects>npm install -g @angular/cli
+$ npm install -g @angular/cli
 ```
 Check your angular version by executing the following command:
 
 ```bash
-C:\projects>ng -v
+$ ng -v
 
 @angular/cli: 1.0.0
 node: 6.10.2
@@ -57,39 +56,34 @@ Execute the following commands.
 
 ```bash
 
-C:\projects>npm install -g cordova
-
-C:\projects>npm install -g ionic
-
+$ npm install -g cordova ionic
 ```
 
-Once the above commands are executed successfully, check the versions of cordova and ionic by executing the following commands.
+Once the above command is executed successfully, check the versions of cordova and ionic:
 
 ```bash
-C:\projects>cordova -v
+$ cordova -v
 7.0.1
 
-C:\projects>ionic -v
+$ ionic -v
 3.4.0
 ```
 
-These are the latest versions as of this writing.
-
-On successful execution of the above commands, you're all set to create your app with Ionic framework.
+You're all set to create your app with Ionic framework.
 
 To create your app, change into the directory where you want your app to reside and execute the following command:
 
 ```bash
-C:\projects> ionic start auth-ng4-ionic3-af2 blank
+$ ionic start auth-ng4-ionic3-af2 blank
 ```
 
->The command ionic start will create the project with name "Ionic_AngularFire2_Project" using "blank" template.
+>The command ionic start will create the project with name "auth-ng4-ionic3-af2" using "blank" template.
 
 Change to the project directory, which was just created with the above command.
 
-> C:\projects\auth-ng4-ionic3-af2>ionic info
+```
+$ ionic info
 
-```bash
 global packages:
 
     @ionic/cli-utils : 1.4.0
@@ -151,40 +145,41 @@ To start your app, execute the following command:
 
 ```bash
 
-C:\projects\auth-ng4-ionic3-af2> ionic serve
-
+$ ionic serve
 ```
 If everything is installed correctly, the app should open your browser with the dev server running at the following url
 **`http://localhost:8100`** and will display default home page.
 
 ### Configuring AngularFire2 and Firebase
 
-Install angularfire2 and firebase by executing the following command in your project directory:
+Install the required packages in your project directory:
 
 ```ts
 
-C:\projects\auth-ng4-ionic3-af2>npm install angularfire2 firebase promise-polyfill --save
+$ npm install angularfire2 firebase promise-polyfill --save
 
 ```
 
-_This should add angularfire2 and firebase entry in your project's package.json file in dependencies section. Something similar_
+_This should add angularfire2, promise-polyfill and firebase entry in your project's package.json file as dependencies. Something similar to:_
 
-> "angularfire2": "^4.0.0-rc.1",
-
-> "firebase": "^4.1.3",
+```
+"angularfire2": "^4.0.0-rc.1",
+"firebase": "^4.1.3",
+"promise-polyfill": "^6.0.2",
+```
 
 ### Setup @NgModule
 
 Open your project in your favourite editor and open the `app.module.ts` file, under `src/app`
 and add the following three entries.
 
->1) Import AngularFireModule and AngularFireDatabaseModule at top.
+1) Import AngularFireModule and AngularFireDatabaseModule at top.
 
->2) Define your firebaseConfig constant.
+2) Define your firebaseConfig constant.
 
->3) Initialize your app, by adding AngularFireModule and AngularFireAuthModule in the "imports" array in @NgModule
+3) Initialize your app, by adding AngularFireModule and AngularFireAuthModule in the "imports" array in @NgModule
 
->4) Also, add AngularFireDatabase in the "providers" array in @NgModule
+4) Also, add AngularFireDatabase in the "providers" array in @NgModule
 
 your `app.module.ts` file should look something like this.