Merge pull request #762 from heniotierra/delay_bug_fix

fix to issue #761
Decouple Crafty.pixelart from individual renderers

Currently `Crafty.pixelart()` explicitly alters the canvas and DOM renderers.  This PR has it fire an event instead.

The canvas and DOM contexts now listen for the event, and make the appropriate changes.  This will make it simpler to add new contexts (like webgl) or to introduce multiple renderers of the same type.

This patch also tracks the current pixelart setting, and ensures that, when a canvas context is inited, that it matches that value.  It doesn't do something similar for the DOM element because the stage is created as soon as you init Crafty.
Merge pull request #765 from starwed/eventify-pixelart

Decouple Crafty.pixelart from individual renderers
All tests invoked from a single file.
Playgrounds are now in their own independent directory.
Merge pull request #763 from grozen/separate-playgrounds

All tests invoked from a single file