decrease container spin to once per test

spec/simple_spec.rb

@@ -49,6 +49,7 @@ RSpec.describe "Simple" do
     let(:name) { "clean_urls" }
 
     it "should drop the .html extension from URLs" do
+      app.run do
         response = app.get("/foo")
         expect(response.code).to eq("200")
         expect(response.body.chomp).to eq("foobar")
@@ -60,6 +61,7 @@ RSpec.describe "Simple" do
         expect(response.body.chomp).to eq("bar")
       end
     end
+  end
 
   describe "routes" do
     let(:name) { "routes" }