Made additional revisions to site- fonts, colors, buttons

[ahruygt]

• Added more padding to the first two divs
• Changed font to "Avenir"
• Added rounded corners to buttons
• Switched out white devices for screen shot of Chris Gannon's work

[ahruygt]

@mglukhovsky There is a chance I didn't push this correctly? @coffeemug can you check that my changes were made?