Extract cucumber env and steps to ease code reuse

producer extensions like producer-rails must not reimplement all the
testing infrastructure, this extraction allows to setup everything with
just one require call in cucumber env:

    require 'producer/core/testing/cucumber'

lib/producer/core/testing/cucumber.rb

@@ -0,0 +1,39 @@
+require 'aruba/cucumber'
+require 'aruba/in_process'
+
+require 'producer/core'
+require 'producer/core/testing/aruba_program_wrapper'
+require 'producer/core/testing/cucumber/etc_steps'
+require 'producer/core/testing/cucumber/execution_steps'
+require 'producer/core/testing/cucumber/output_steps'
+require 'producer/core/testing/cucumber/recipe_steps'
+require 'producer/core/testing/cucumber/remote_steps'
+require 'producer/core/testing/cucumber/ssh_steps'
+
+# Raise aruba default timeout so test suite can run on a slow machine.
+Before do
+  @aruba_timeout_seconds = 8
+end
+
+# Use aruba "in process" optimization only for scenarios not tagged @exec.
+# We need a real process in a few cases: real program name, interactive usage…
+Before('@exec') do
+  Aruba.process = Aruba::SpawnProcess
+end
+
+Before('~@exec') do
+  Aruba::InProcess.main_class = Producer::Core::Testing::ArubaProgramWrapper
+  Aruba.process = Aruba::InProcess
+end
+
+# Fake home directory for @fake_home tagged scenarios.
+Before('@fake_home') do
+  ENV['HOME'] = File.expand_path(current_dir)
+end
+
+# Enable cucumber-sshd "fast" mode (persists sshd across scenarios), and
+# register hooks for @sshd tagged scenarios.
+Before do
+  @_sshd_fast = true
+end
+require 'cucumber/sshd/cucumber'