nest divs for easier styling; center adorable icons

i'll leave line-by-line comments in my PR with explanations :) 
a few things happened in `#icons`:

```css
clear: both; // probably don't need this, but it clears any lingering floats
text-align: center; // aligns the ul element in the center
width: 100%; // occupies the entire section element
margin-top: 50px; // adds a margin because i thought it was pretty that way :)
```

:balloon: