Add apple-touch-icons

Naming and sizes from here http://mathiasbynens.be/notes/touch-icons.

Note: I think the "changes" to the *.md files is because I'm on a mac. I wasn't able to find a solution to it, so I committed what it thought I changed. It could be something in the .gitattributes file like [this stackoverflow question](http://stackoverflow.com/questions/12205846/git-shows-random-files-as-modified-after-clone-cant-discard-them) says, but I didn't see markdown in there.

I've also added the .psd to `img/wpd_favicon.psd` so you can make changes too.