Different branch to handle button click not responding issue.
A workable solution.  Giving height to GridView from MainViewController.
Adding animation.
Add delegate demo.
Added delegate for cellTapped event.
Added classes for testing notification sound.
Process sound.
Can now play system sound normally using UILocalNotification.
Start from mainviewcontroller
Merge branch 'fix-button-not-responding'
Merge back button not responding bug fix branch.