Front Page Design Updates

[cycomachead]

I think we can make the front page feel a little easier to use.

• [ ] only show at most 3 buttons, not 5.
• [ ] We shouldn't link to the PDF reference manual
• [ ] Consider reducing the spacing around the banner?
• [ ] Snap! banner backgrounds should be white?
• [ ] carousels should show 6 projects and reflow to 2x3 on very small screens.
• [ ] Should small screen carousels only show prev/next controls, and not first/last? (2 buttons vs 4) Should they be larger?
• [ ] Should we show alonzo saying welcome? There is no alonzo anywhere....