Fixes Issue #11

1.  Redefines "retina" to be `window.devicePixelRatio >= 1.5`
2.  Checks the `classes` property of `settings.retina` and `settings.touch` before adding " no-retina" or " no-touch" to the `<html>` element's `class` attribute

NOTE:  I didn't edit the minified version. I assume @markgoodyear or @toddmotto will handle that with whatever compressor/minifier tool they've used before.