<ons.Page> has events that will be fired at certain part of DOM life cycle. These events help in performing certain functions.
init : Is fired once the <Page> attaches to DOM. This is used only for initializing the app.
destroy : Is fired after the <Page> detaches from DOM. This is used for memory clean up.
show : This event is fired, once the <Page> comes to view,
hide : This event is fired, once the <Page> moves out of the view but exists in memory
