add vertical center file
Merge branch '2.x.x' into 2.x.x-vertical-center
Add in vertical midpoint settings
Remove Compass dependency
Adding documentation.
Check for Compass/Bourbon mixins
Merge from current parallax
Merge branch '2.x.x' into 2.x.x-vertical-center

* 2.x.x:
  Missing elements
  Tint/Shade Stack Colors function added to allow for dark to light progression
  Resolves #54
  Resolves #58
  Updated parallax to work with prefixing mixins if they're available
  Proper version bump

Conflicts:
	compass/stylesheets/toolkit/_parallax.scss