Use the new Docker queue

faster better stronger
Merge pull request #1784 from joshk/patch-1

Use the new Docker queue
Fix all kinds of typos.
Make core tests pass on sass 3.4.
Utility method to assert valid keys.
Add basic asset collection configuration via ruby and use it for image urls.
Use asset collections and asset resolver for fonts.
Use the asset resolver for generated images.
Refactor stylesheet_url with better tools and remove useless code.
Allow sass-based configuration of asset collections.
Put sass files from an asset collection on the load path.