v3

[mdo]

Figured I'd spent a couple hours bringing Preboot up to speed with some things. Here's what's new:

• Switch from Less to Sass
• Rewrite docs in Markdown
• Redesign docs site
• Update Normalize to latest release
• Drop almost all vendor prefix mixins (use Autoprefixer instead)
• Add new container mixin
• Update readme to show latest information
• Remove Makefile and use Jekyll's built-in Sass compiler

Needs a bit more testing, and I could probably include/remove a few more things. Will noodle on it more.

---

• Fix up docs snippets to improve mobile scrolling

[matthewpizza]

@mdo Related to #53, it would be rad to have grid and offset mixins with optional media queries (i.e. usage similar to the Bootstrap make-xs-column mixin). This could be handled with the current mixins by using the @if control structure:

@if $screen-width != false {
  // do the media query
} @else {
  // don’t media query
}

Or, alternatively, by creating separate “no media query” mixins for discoverability (and maybe performance).