Reorganization

# Changes
 - Organizes patterns into components, modules, and regions.
 - Improved scroll indicator performance (throttled; more efficient finding which element to highlight).
 - Removed unused `.embed-container` pattern (duplicate of `.media-video`).

For review: @DoSomething/front-end

I still argue that some of these are more modules than components. *Components* would be items that are typically small parts of a larger whole, and don't usually stand alone outside of a module. *Modules* would be items that can contain components as well as other modules and are typically larger items. Of the above components I would argue that `tile`, `polaroid`, `pullquote`, `message-callout`, `media-options` could potentially be standalone modules instead.