Add ui time text element which automatically formats time and handles time units
Add TimeText docs
Add link to the three.js Vector2 documentation
Merge branch 'feature-time-text-element' into develop
Change Stage into a Window mixin
Change Window to mixin Stage
Mark Card and Menu as not dynamic Windows
Export UI Window instead of Stage
Update demo app.js to use Window instead of Stage
Update Stage docs to refer to Window
Add Element animate docs
Merge branch 'feature-rename-stage' into develop