add unicorn configuration to hanami integration app

The tests attempt to invoke hanami with unicorn, but the
unicorn configuration for hanami was missing resulting in failure.

integration/apps/hanami/config/unicorn.rb

@@ -0,0 +1,23 @@
+require 'datadog/demo_env'
+
+# config/unicorn.rb
+worker_processes Integer(ENV["WEB_CONCURRENCY"] || 3)
+timeout 15
+preload_app true
+
+Datadog::DemoEnv.print_env('Unicorn master environment')
+
+before_fork do |server, worker|
+  Signal.trap 'TERM' do
+    puts 'Unicorn master intercepting TERM and sending myself QUIT instead'
+    Process.kill 'QUIT', Process.pid
+  end
+end
+
+after_fork do |server, worker|
+  Signal.trap 'TERM' do
+    puts 'Unicorn worker intercepting TERM and doing nothing. Wait for master to send QUIT'
+  end
+
+  Datadog::DemoEnv.print_env('Unicorn worker environment')
+end