refactor stage, element
update readme
fix buffered rendering
refactor sprite
fix sprite mode setting
add toroidial stage support
add Stage.at method
update readme for sprites
add layer support
update readme
fix height/width change issue for default element rendering
implement clock example
implement init object in element constructor
make drawing centering independent of element size
add moveTo method to elements
implement update chaining via naive method
implement update chaining in memory-efficent way
add event listening for elements, enhance debug stuff
fix numeral spacing in example
use document to listen for events