Issue title: How to make it working in webpack?
 Issue body: There is no example to include it with webpack (angular-cli) template.

I followed the toast notification documentation to add the SimpleNotificationComponent in the module
Then in the component, I injected the notificationService to call it.

However, there is no issue in running webapack build but I am getting the below error.
metadata_resolver.js:227Uncaught Error: Unexpected directive 'SimpleNotificationsComponent' imported by the module '....Module'

What could be the issue? Is there a better example to use it in a webpack template or angular-cli template?

 Comments: 
 Comment 0: Hi,
 I am in the process of creating an application template using CLI and some of the libraries. For a simple example have a look at my new template repository. https://github.com/olakara/ng2-app-template
I have added the angular2-notifications to the CLI based application.

 Comment 1: Hi, I get it working and here is what to do,

In the module,
import {SimpleNotificationsModule, PushNotificationsModule} from 'angular2-notifications';
and add the modules into imports:[....]

In the component, include the tag in the component.html
<simple-notifications [options]="options" (onCreate)="onCreate($event)" (onDestroy)="onDestroy($event)"></simple-notifications>

then in the component to add the below declaration
import {NotificationsService, SimpleNotificationsComponent} from 'angular2-notifications';
and add the NotificationsService in the constructor, 
and show notification by calling this.notificationService.success("title", "...");

Thanks.
 Comment 2: It works on development mode, but when try to generate a distribution version using `UglifyJsPlugin` it triggers an error:

```sh
ERROR in app.c3b86f6b3725dad90c4b.js from UglifyJs
SyntaxError: Unexpected token: name (NotificationsService) [app.c3b86f6b3725dad90c4b.js:11,6]
```
 Comment 3: I follow @xinzhang solution and I found this almost 100% accurate to my project build with webpack. TY @xinzhang ! :+1:  


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