Grunt tasks

This is a contrast to #256, which uses concurrent console tasks to accomplish file concatenation and Shopify's theme gem activity.

This method uses `grunt-shopify`, as purposed in another discussion. 

- All styles are separated into a `stylesheets/` folder
- `stylesheets/` folder is watched and concatenates to `assets/timber.scss.liquid`
- Run `grunt` to concatenate files on save, optimize images, and upload to your store
- Run `grunt build` to concat files and optimize images
- Run `grunt deploy` to build and deploy all theme files to your store
- Run `grunt zip` to generate a Shopify-friendly zip file with only the required files

New Folder Structure:
```
├── various config files
├── src
│   ├── stylesheets
│       ├── timber.scss.liquid
│       └── various global/partial/module stylesheets
├── assets/
├── layout/
├── snippets/
├── templates/
```

Kudos to @graygilmore for getting the jump on this implementation.

cc/ @stevebosworth @Shopify/fed @fredryk