* Add Assets.xcassets to MessageKitAssets.bundle
* Replace incomingGray, outgoingGreen, inputBarGray
* Replace playButtonLightGray, with UIVisualEffectView to mimic iMessage (Fixes#1321 , Fixes#1335)
* Fixes an issue where the triangle in the play button is not centered
* remove sendButtonBlue, add incoming/outgoingAudioMessageTint
Matches audio tint more closely to iMessage by tinting white on outgoing and tinting blue on incoming
* Remove backgroundColor, add collectionViewBackground
* remove unused labelColor
* Remove unused placeholderTextColor
* Remove grayColor
* remove darkTextColor, add typingIndicatorDot
Matches dot color more closely to iMessage
* Remove unused lightGrayColor
* Adds high contrast appearances to the color assets
* Add MessageKitError string for case when color asset could not be loaded
Also removes redundant internal access level modifier on MessageKitError (internal is default), and changes MessageKitError from enum -> struct as its members were not enum cases
* Fix swiftlint issues
* Add label color asset and use in ContactMessageCell
* Fix tests
Kino Roy
zhongwuzw
Javier Cancio
Steven Deutsch