apple-touch-icon-precomposed gets manipulated anyway if it includes alpha channel

[zrisher]

Hi there,

Great repo! Working with this advice myself, I've noticed that my apple touch icons were being manipulated by iOS and the background turned black. This turned out to be because I was trying to use alpha channel transparency in those pngs - not allowed apparently! I had to create new icons and replace the transparency with a background color.I found this tool useful for my precomposing: http://www.gieson.com/Library/projects/utilities/icon_slayer

I'd recommend perhaps adding clarification on this point to the section on favicon generation.