Added sections on Metal API and shading language
Added my article Scene Kit

I think that I'm resonably ok with the article by now.

Note that I added a link to the book page under "further reading".
Remove it if you want to.

(sorry that the linked GIFs are so large)
Add initial 'elegant game design' article draft
A few small copy changes
Merge pull request #60 from warrenm/issue-18

Metal Article (Combined)
Merge branch 'master' of https://github.com/d-ronnqvist/articles-private into d-ronnqvist-master
Merge branch 'd-ronnqvist-master' into issue-18
I am committing my article on sound design for the gaming issue of Objc-io.
Edits 1
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Update images
Merge pull request #62 from lazerwalker/issue-18

"Elegant Mobile Game Design" article
Some more minor copy changes to 'Elegant Game Design'
Merge pull request #63 from lazerwalker/issue-18

More minor article changes
added "Multipeer Connectivity in Games" article
updated link to ConnectionManager.swift
fixed author tag quote escaping
Edits 1
Edits 2