specify rspec ~> 3.0
refactor the way imported_assets are added to the sitemap

- importing all images/fonts is moved to a separate method and run after_configuration. they get added to the imported asset list now
- assets handle their own resolution & directory manipulation using the passed in context from the app/sprockets_env
- assets will remove their “asset type” directory if it is in the logical path so they will be moved to the correct directory from config
- the output_path for an imported asset is now a bit more flexible to be a proc/labmda with or without arity
use Thor::CoreExt::HashWithIndifferentAccess instead of Openstruct to keep away from ruby 1.9.3 behavior difference
add skip tag for ruby 1.9.3 to skip specs expecting certain behavior from proc arity
use Middleman::Util.recurively_enhance vs. Thor:Corext::HashWithIndifferentAccess
Merge pull request #67 from stevenosloan/prevent_duplicate_imported_assets

Prevent duplicate imported assets