Add sass-rails dependency
Blacklight 5.2 removed the sass-rails dependency, but we need it
loaded for rails 3.2.  Typically it's injected into the host app's
gemfile when doing `rails new`
Merge pull request #160 from projecthydra/sass-rails-dep

Add sass-rails dependency
ActiveFedora::Base#accessible_by relation to filter results based upon cancan ability and action
Change order of parameters to #gated_discovery_permissions to be consistent with #apply_*_permissions methods