Clean up CSS queries for progresive enhancement

- Removed max width for small-wide media query
- Removed the need to use head conditionals for IE and went with
progressive approach for browsers that understand nth-child
- Included medium third-center resizing option to have the center item
take up more space
Update
Merge branch 'master' of https://github.com/ngoodrum/FluidResponsiveGrid

Conflicts:
	README.md