**Swift 4.0
NOTE: A custom UIButton with a spinner animation
NOTE: This repesitory is a fork from the original TKSubmitTransition. I didn't make the library, I only migrated it to Swift 4 and fixed the migration issues and added some features.
Inpired by https://dribbble.com/shots/1945593-Login-Home-Screen
btn = GCSpinnerButton(frame: CGRectMake(0, 0, 44, 44))