Support Sprockets 2.12.x
Refresh gemspec
Ensure importer accepts context reference
Merge pull request #274 from rails/support-sprockets-2-12

Support Sprockets 2.12.x
Merge branch '4-0-stable' into merge-4-0-stable-into-master

Conflicts:
	lib/sass/rails/importer.rb
	sass-rails.gemspec
	sass-rails.gemspec.erb
Include rails