Improvements (triage me)

[nrichards]

• add support for injecting an image at an arbitrary location
• support a 2x2 matrix of generated images
• support grouping button ranges so that when animated all the buttons in a range will flash simultaneously
• consider extending the HTMLtoken so that you can pass image options (gif size) and markdown formatting options (inject preceding line break) in with a tag that is made invisible through normal markdown rendering
• support total removal of a button, when you encounter a "/" slash or an "or", like flash but for alternates
• add hold delay at beginning
• add 100% frame as start frame for printing