docs(@angular/cli): add application environments

docs/documentation/stories.md

@@ -22,4 +22,5 @@
  - [Corporate Proxy](stories/using-corporate-proxy)
  - [Internationalization (i18n)](stories/internationalization)
  - [Serve from Disk](stories/disk-serve)
- - [Code Coverage](stories/code-coverage)
+ - [Code Coverage](stories/code-coverage)
+ - [Application Environments](stories/application-environments)

docs/documentation/stories/application-environments.md

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+# Application Environments
+
+## Configuring available environments
+
+`.angular-cli.json` contains an **environments** section.  By default, this looks like:
+
+``` json
+"environments": {
+    "dev": "environments/environment.ts",
+    "prod": "environments/environment.prod.ts"
+}
+```
+
+You can add additional environments as required.  To add a **staging** environment, your configuration would look like:
+
+``` json
+"environments": {
+    "dev": "environments/environment.ts",
+    "staging": "environments/environment.staging.ts",
+    "prod": "environments/environment.prod.ts"
+}
+```
+
+## Adding environment-specific files
+
+The environment-specific files are set out as shown below:
+
+```
+└── src
+    └── environments
+        ├── environment.prod.ts
+        └── environment.ts
+```
+
+If you wanted to add another environment for **staging**, your file structure would become:
+
+```
+└── src
+    └── environments
+        ├── environment.prod.ts
+        ├── environment.staging.ts
+        └── environment.ts
+```
+
+## Amending environment-specific files
+
+`environment.ts` contains the default settings.  If you take a look at this file, it should look like:
+
+``` TypeScript
+export const environment = {
+  production: false
+};
+```
+
+If you compare this to `environment.prod.ts`, which looks like:
+
+``` TypeScript
+export const environment = {
+  production: true
+};
+```
+
+You can add further variables, either as additional properties on the `environment` object, or as separate objects, for example:
+
+``` TypeScript
+export const environment = {
+  production: false,
+  apiUrl: 'http://my-api-url'
+};
+```
+
+## Using environment-specific variables in your application
+
+Given the following application structure:
+
+```
+└── src
+    └── app
+        ├── app.component.html
+        └── app.component.ts
+    └── environments
+        ├── environment.prod.ts
+        ├── environment.staging.ts
+        └── environment.ts
+```
+
+Using environment variables inside of `app.component.ts` might look something like this:
+
+``` TypeScript
+import { Component } from '@angular/core';
+import { environment } from './../environments/environment';
+
+@Component({
+  selector: 'app-root',
+  templateUrl: './app.component.html',
+  styleUrls: ['./app.component.css']
+})
+export class AppComponent {
+  constructor() {
+    console.log(environment.production); // Logs false for default environment
+  }
+  title = 'app works!';
+}
+```
+
+## Environment-specific builds
+
+Running:
+
+```
+ng build
+```
+
+Will use the defaults found in `environment.ts`
+
+Running:
+
+```
+ng build --env=staging
+```
+
+Will use the values from `environment.staging.ts`