checks if active record responds to 'joins', so this can work with in…

…ternuity's quick_scopes gem; added .swp files to git ignore

.gitignore

@@ -1,3 +1,5 @@
+*.swp
+**/*.swp
 *.gem
 Gemfile.lock
 .bundle

lib/cancan/active_record_additions.rb

@@ -21,7 +21,7 @@ module ClassMethods
       # internally uses Ability#conditions method, see that for more information.
       def accessible_by(ability, action = :read)
         query = ability.query(action, self)
-        if respond_to? :where
+        if respond_to?(:where) && respond_to?(:joins)
           where(query.conditions).joins(query.joins)
         else
           scoped(:conditions => query.conditions, :joins => query.joins)