Master tracker issue - ITI and subtasks to be filed by @dvoytenko
Details: https://docs.google.com/presentation/d/1z-a6Hxy3XIjRCAb4ExuFTe3AsLUsRRBezGyU3cVvwC0/edit#

Items:

• selector support
• multiple target support
• full CSS syntax for timing
• introduce var() and calc()
• sub-targets
• rand
• width and height
• full API
• animation composition
• extract keyframes from styles