IE8 bug fixes, code cleaning

[cshold]

• IE8 defaults to the handlebar.js cart template in the ajax modal and drawer because it doesn't support jQuery's .load function
• IE8 fires a resize event all the time, so now it's excluded for updating the modal size
• Took window scroll into account when aligning modal close button
• IE8 modal now has an overlay you can see
• Resize and onorientationchange are only initialized once
• Added modal overlay and close button to the setup function where they belong
• Transition mixin no longer breaks with multiple arguments, just use quotes when passing in the transition
  • E.g. @include transition('background-color 100ms ease-in-out, margin 100ms ease-in-out');