Responsive plugin v0.5 items

[mattpass]

• Add nth child pseudo to CSS but scan existing text without (so user can choose to remove nth-child from selector)
• Line highlight media query line with same responsive bar background color
• Highlight lines that have been changed in the CSS with appropriate color (including inheritance - eg 800px is yellow and 700px is blue. If you have a style for something that's width: 100px and change it to 50px under the 800px media query, that line will turn yellow, but the 700px section the line containing the same style will also turn yellow. This way we know where it's inherited from. If we change it within the 700px media query to 40px, it would turn from yellow to blue).