Update for Sass Module System

[J. Ryan Conklin]

Issue

Update Particle's default sass code to implement module system.

Analysis

Particle's default sass structure is tightly managed to reduce duplicated sass. The new module system from Sass reduces this complexity.

http://sass.logdown.com/posts/7858341-the-module-system-is-launched

Confirmation

As a developer, my sass is captured in modules and I do not forward duplicate sass through my system.