Use system specs instead of feature specs

We get rid of database cleaner, and JavaScript tests are faster because
between tests we now rollback transactions instead of truncating the
database.

spec/shared/system/progressable.rb

@@ -0,0 +1,45 @@
+shared_examples "progressable" do |factory_name, path_name|
+  describe "Progress bars", :js do
+    let!(:progressable) { create(factory_name) }
+    let(:path) { send(path_name, *resource_hierarchy_for(progressable)) }
+
+    scenario "With main progress bar" do
+      create(:progress_bar, progressable: progressable)
+
+      visit path
+
+      find("#tab-milestones-label").click
+
+      within("#tab-milestones") do
+        expect(page).to have_content "Progress"
+      end
+    end
+
+    scenario "With main and secondary progress bar" do
+      create(:progress_bar, progressable: progressable)
+      create(:progress_bar, :secondary, progressable: progressable, title: "Build laboratory")
+
+      visit path
+
+      find("#tab-milestones-label").click
+
+      within("#tab-milestones") do
+        expect(page).to have_content "Progress"
+        expect(page).to have_content "Build laboratory"
+      end
+    end
+
+    scenario "No main progress bar" do
+      create(:progress_bar, :secondary, progressable: progressable, title: "Defeat Evil Lords")
+
+      visit path
+
+      find("#tab-milestones-label").click
+
+      within("#tab-milestones") do
+        expect(page).not_to have_content "Progress"
+        expect(page).not_to have_content "Defeat Evil Lords"
+      end
+    end
+  end
+end