A myriad changes

1. Added function that removes SVG images in browsers that don't
support them.
2. Added SVG images for select elements and cart icon.
3. Updated normalize 3.0.0 to 3.0.1
4. Added greek letter class names to style h1-h6.
5. Added CSS to style form elements.
6. Changed media queries for browsers that don't support rem units.
7. Added utility classes to stylesheet to align text, hide and reveal
elements based on device size, etc.
8. Added CSS for tags.
9. Added CSS to style select elements using SVG.
10. Added theme settings for color and size of text, colour of links,
and background color.
11. Layed-out header and footer for theme to look half-decent.
12. Layed out Cart page, and made it work on mobile devices too.