Merge pull request #35 from playcanvas/master

merge
Merge pull request #36 from playcanvas/master

merge
DXT1/DXT5 DDS support. Normal maps can be packed into DXT5nm (a bit differently swizzled) now.
Added pc.math.log2, because Math.log2 is not supported on IE.
pc.math.log2
Fix
DXT cubemaps and different IE check.
Non-compressed RGBA dds support.
Fixed non-square DDS textures.
More conventional DXT5nm swizzling.
pc.math.log2 changed to Math.log2 patch
Fix
Merge pull request #135 from guycalledfrank/feature/dxt

Feature/DXT