Fix context switch and filter inheritance
Merge pull request #22 from gameclosure/fix-ctx-switch

Fix context switch and filter inheritance
Update current shader index before calling tealeaf update
Merge pull request #23 from gameclosure/fix-shader-order

Update current shader index before calling tealeaf update
Add missing shader bind to clearRect
Merge pull request #24 from gameclosure/fix-clear-shader

Add missing shader bind to clearRect