NotificationBanner Release v1.2.0

Changes:

• NotificationBanner's now have a isDisplaying boolean property which will tell you wether or not the banner is currently being displayed.

• The NotificationBannerQueue is now a public class that can be accessed via:

let bannerQueue = NotificationBannerQueue.default

As of right now, the only thing that can be obtained from the banner queue is a property called numberOfBanners which tells you how many notification banners are currently on the queue.

New CocoaPods Release: v1.2.0 ✅
Closes #8 🎉
Thanks @JoniVR! 👍