added site screenshot

Author: abhishekkhandait

README.md

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 This project was generated with [Angular CLI](https://github.com/angular/angular-cli) version 1.0.1.
 
+![alt text](https://github.com/abhishekkhandait/Angular2-Task-board/blob/master/images/demo.png)
+
 ## Development server
 
 Run `ng serve` for a dev server. Navigate to `http://localhost:4200/`. The app will automatically reload if you change any of the source files.