Prevents pollution of global namespace in SP.

Adds anonymous function wrapper around core SP code, preventing global
namespace pollution.
Merge pull request #8 from rhyolight/js-scope-cleanup

Prevents pollution of global namespace in SP.
Move to CanvasRendered by default; Re-use sprites and update textures ever iter
Move mod bug fix inside closure
Merge pull request #9 from iandanforth/bugFixes

Move to CanvasRenderer by default; Re-use sprites and update textures ev...
Add example with two layers; Fix bug in building final output array
Merge pull request #10 from iandanforth/twoLayers

Add example with two layers; Fix bug in building final output array
Added .gitignore file