-[ ] CallScreen
-[x] functional button
-[ ] needs design
-[ ] disable other contact call buttons while in call
-[ ] iOS11
-[x] resize nav content
-[ ] background showing at top of all vc's
-[] iPhoneX
-[x] use differently sized banner for now
-[] mimic X system design
-[ ] iOS10
-[x] resize nav content
-[ ] animation glitch while push/pop
-[ ] iOS9
// FREEBIE