Add rubocop spacing rules

We were following these rules in most places; we just didn't define them
anywhere.

spec/models/concerns/sluggable.rb

@@ -15,15 +15,15 @@ shared_examples_for "sluggable" do |updatable_slug_trait:|
     context "slug updating condition is true" do
       it "slug is updated" do
         updatable = create(factory_name, updatable_slug_trait, name: "Old Name")
-        expect{updatable.update_attributes(name: "New Name")}
-          .to change{ updatable.slug }.from("old-name").to("new-name")
+        expect { updatable.update_attributes(name: "New Name") }
+          .to change { updatable.slug }.from("old-name").to("new-name")
       end
     end
 
     context "slug updating condition is false" do
       it "slug isn't updated" do
-        expect{sluggable.update_attributes(name: "New Name")}
-          .not_to (change{ sluggable.slug })
+        expect { sluggable.update_attributes(name: "New Name") }
+          .not_to (change { sluggable.slug })
       end
     end
   end