Merge pull request #21 from bhollis/master

Fix file-change tests and compatibility with latest Sprockets.
have sprockets add images directory when looping through asset try_paths
map images_dir to Middleman sprockets
added response code step to server_steps
cucumber test coverage for sprockets images
Failing test for issue #19
Add a sitemap manipulator based on @jordanandree's work to copy images and fonts into the build output.
Properly integrate Sprockets and Compass/Sass so they use our asset methods.

We no longer need any custom Sass stuff, they all work together automatically. Fixes issue #19, and may fix some of #336.
Fix tests and add a couple new in-progress tests
Allow users to directly add paths to Sprockets and properly invalidate the sitemap when they do. Deprecate :js_assets_paths.
Finish fully connecting Sprockets to Middlean.

Helpers are now properly plumbed through, app current_path is correctly set for all assets no matter what, asset exceptions during build show up as errors instead of being written into the asset content.
Require build success on 2.0.0
Don't forget to add fonts to the asset load path
Clear out sass cache and fix tests
Add "?body=1" only once
Merge pull request #24 from igoralekseev/patch-1

Add "?body=1" only once
prep
Add an in-memory cache for Sprockets assets.

For some reason Sprockets defaults to no cache, so any change to an asset requires rebuilding all assets. This really hurts for big single-page JS apps. Adding a hash-based cache fixes that. This was figured out by @jvaill, thanks! Fixes middleman/middleman#734.