Update to and support timestep v2.1.0

[lunarraid]

Release notes:

• When in Canvas mode, filtered textures are now cached for better performance
• loader now has a progress property
• Preloading audio is now supported in browser, by providing an Array of individual mp3 urls to the preloader
• Rendering logic has been overhauled, using matrix transform objects for optimization
• WebGL support is now available in browser, by adding useWebGL: true in the manifest under browser -> canvas
• Splash screens now show properly in the browser during game load
• Hyphenated font names now load correctly in browser