Only bitmask transparency when "transparent" option enabled.

[waruyama]

When selecting the "transparent" option, I would expect bunnymark to use alpha transparency for blending over the background. Instead seems to use bitmask transparency and looks like this:

Unlike the animated bunnys, the bunnys at the bottom have full alpha transparency.

Would it be possible to add an option for switching between alpha and bitmask transparency. I know almost nothing about WebGL, yet, but my project would required full alpha transparency for sprites, so this issue report doubles as a question if alpha transparency with sprites is possible at all.