Changed the renderableLists object to be an array

Was unnecessarily a list before
Removed unused imports
Changed the Store class to be static- reduces unneccesary object
instantiation
Merge pull request #9 from factorsofx/master

Small performance improvements, Store class is static

The changes related to the Store class make so much sense I can't believe it wasn't already like that. Thanks for spotting that! About the RenderablesList, I think at some point I thought I would let setNumberOfLayers to be called any time, but I don't think that would make much sense after all. Thanks, again! - Diogo