Added device images:

- iPhone 6 (img/iPhone.svg)
  original image from http://www.graphberry.com/item/free-iphone-6mockups/
- iPad (img/iPad.svg)
  original image from http://dtailstudio.com/mobile-devices

Exported using SVG 1.1 with fonts converted to outlines.
Compatibility chart: http://caniuse.com/#feat=svg
Changed JSHint options:

- removed 'latedef' to allow for circular functions in the instructions.js file (admitedly bad practice)
Added iPhone 6 screenshots from Simulator
Optimized iPhone screenshots (720.2 KB -> 482.2 KB ; 33%)
Updated image info in Codekit config
Added iPhone device image
Implemented screen changes for iPhone
Implemented fading between preview images
Starts with no device shown, then loads up device image when selected
Merge branch 'master' into gh-pages

Conflicts:
	config.codekit