New delegate methods and footer button addition

[BadhanGanesh]

What's New:

• Added new properties - shouldFooterBehaveAsButton, footerButtonColor.
• Added new delegate methods - didClose, didTap.
• Documentation changes.
• ReadMe changes.
• Now changing UI-related public attributes will reflect immediately in screen.
• Footer Label can now act as a button
  • This can be used to resend otp from server.