Comparing of transparent pixels is broken in iojs 3.0.0

[LinusU]

For some reason two very similar images that contains semi-transparent pixels are considered different.

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[LinusU]

Smaller example, enlarged 8x:

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[LinusU]

This is how the images looks next to each other in Gimp, with a red background added.

One can see that there is a small small variance in the shading. I have the tolerance set to 5 however so that should work.

The strangest part about all this is that it works in Node.js 0.12 but not on iojs 3.0.

[SevInf]

Should be handled by #12

[sipayRT]

@LinusU can you check it now with v3.1.0?